Communication Mediums for Signal, ITS, and Freeway Surveillance Systems: Final Report (1996)

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A.~.7 Commercial Communication Services Commercial services have ITS applications and win be increasingly Important as Advanced Traveler Formation Systems (ATIS) are deployed. Historically, implementation/operation of Advanced Traffic Management Systems (ATMS) has not found commercial infrastructure to be cost competitive wad private networks, as indicated in He survey conducted as a part of Phase of this project. This section win address: · Rates for Commercial Services Satellite Communications Broadcast SubcalTiers for ITS Commercial Wireless Services, and ISDN. A.~.7.1 Rates for Commercial Services Rates for commercial services vary widely by geographic area and service provider. This section win briefly summarize rates that have some consistency nationwide. Table A.~.7.! presents representative cellular rates. Depending on preferences, users may select monthly access rates, peak/off-peak, and nightly rates; including free minutes in the monthly access rate; and/or including a service contract. Table A.~.7.~-2 presents wireless data service rates. Emerging CDPD services win influence these rates in He future. Table A.~.7.~-3 presents ISDN rates. L:\NCHRP\Phasc2.rpr\ NCHRP3-51 · Phase2F~nalReport A1-255

Table A.~.7.1 Representative Cellular Rates | Average Monthly Access | $30 - $189 per month | Peak per/minute . | $.25 - $.60 per minute | Off-peak per/minute | $.05 - $.030 per minute Night $0 - $.30 per minute Included free minutes ~ Peak 0 - t200 Night 0 - 200 Offpeak 30 - 100 Service contract (years) 1 - 3 years . ~ Peak: 7:00 am - 8:00 pm, Monday - Fnday Offpeak: 8:00 pm - ~ ~ :00 pm, Monday - Fnday 7:00 am - Il:OO pm, Weekends Night: Il:00 pm - 7:00 am, 7 days Table A.~.7.~-2 Wireless Data Service Rates Monthly Rate $ | kilobytes | , _ ARDIS $19.95 20 _ $50.00 150 $100.00 350 $190.00 750 _ RAM $25 100 $65 200 $88 275 _ $135 500 CDPD _ Amentech $20 100 $55 500 $99 1,000 AT&T $15 50 $50 500 $ each additional kilobyte $.54 $.35 $.33 $.31 $.27 $.20 $.11 $.10 $.11 to$.16 $.08  L:WCHRP\Phase2~pt\ NCHRP3-51 · Phase2FmalReport A1-256

Table A.~.7.~3 tSDN Rates Monthly Access Rate ~ Per Minute Basic Rate Circuit (BRI) $19 - $90/month $.00 - $.15/minute 2B ~ D = 2 x 64 + 16 = 144 (Typically standard ~WP) kbps Primary Rate Circuit ~ $1,000/month Nl/A 23B ~ D = 1.544 Mbps (Requires 2 TWP) ISDN circuits have various combinations of B (bearers channels and D (data) channels. Normally, one D channel is provided for network control/monitoring/connection functions; however, the B channels can be configured as individual voice channels or consolidated for higher speed data access. Often these special configurations require telephone company configuration support, and perhaps additional charges. The traffic on T} and SONET/fiber circuits varies Widely. For this reason, we have not included pricing data. Local service providers can provide pricing information. With passage of the 1996 Telecommunications Act, a competitive environment may soon emerge, drastically changing services, provider options, and prices. (This space intentionally left bland) ~wCHR~.rpt\ NCHRP 3-51 · Phase 2 Fmal Report A1-257

A.~.7.2 Satellite Communications by Comsat Laboratones CIarksburg, Maryland A. 1.7.2. 1 Satellite Alternatives and ITS Applications There are many areas in which satellite communications can be applied to ITS, often providing the best solution to a problem. The applications can be categorized into several areas. Table A.~.7.2.~-1 presents five broad applications of satellite communications, with specific examples of each. A.~.7.2.2 SafeIIife Performance Charaeferisfics This section covers We venous aspects of a satellite system and Weir effects on We overall performance character~shcs. Initially, the key features of sateHite-based communications are presented. Then, a discussion is offered on We ~eory/concepts of satellites as a communication medium. This is followed by short explanations of We various aspects of a satellite system such ., as orbits, satellite frequencies, channel bawds, typical digital bit-rates, and coverage capabilities. Key features of satellite-based communications There are many unique advantages to using sateDite-based communications. The key features of sateUite-based communications (as compared to terrestrial commurucabons mediums) are presenter! In Table A.~.7.2.2.~-~. L\NCHRP\Phase2.rpt\ NCHRP3-51 ~ Phase2FinalReport A1-258

Table A.~.7.2.~-1 Applications of Satellite Communications to ITS 1 2 Applications Broadcast Information (Could be transmitted to specific regions or broadcast nationally.) Data collection (Sensors could be rapidly deployed to areas of concern or interest without reworking a ground network.) 3 Transmission of control information (To specific sites or groups of sites.) Examples Comments . _ . Highway Advisory Including delivery of: Traffic flow Radio data, road conditions, detour information, other public service information Transmission of Including delivery of: Weather weather-related data forecasts and current road conditions (raintsnow storms, icy roads, high winds, low visibility, and other weather-related phenomena which impedes traffic) Traffic-related video Including delivery of: Detour maps'  information hazardous-area maps, traffic congestion (video/maps), and other visual information _ Traffic flow-rate Report traffic flow information for sensors critical sections of highways (congested areas, construction zones, etc.) . _ Weather-related Indicate when roads are freezing, sensors flooded' experiencing high-winds, or low-visibility Highway Issue regular reports on the status superstructure stress of bridges, tunnels, overpasses, monitoring sensors and other vulnerable structures Smart signs Notify travelers of traffic congestion and suggest alternate routes Traffic flow control Include changing traffic light timing devices or controlling various traffic control-gates, based on traffic flow data National roadside Dropped off and set-up within assistance phones minutes Collision activated Transmit distress beacon to a distress beacons national reaction center along with precise location of vehicle Highway officials and Broad range of transmission rates' law enforcement from low (modem-type) data to personnel voice transmissions, up to a full T1-rate for backbone data services 4 Emergency/distress · . communlca. :lons services 5 Two-way voice/data · - communications L:\NCHRP\Phase2.rpt\ NC~P3-51 · Phase2FmalReport A1-259 I

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Theory/concepts of satellites as a communication medium In general, a satellite may be considered to be a distant radio-freguency ~F) communications repeater that receives upland transmissions and re-transm~ts them in its downlink beams. Figure A.~.7.2.2.2-! illustrates the end-to-end communications required in establishing a satellite link. The link is shown in its most generic form with transmit and receive capabilities at both ends. Such facilities are characteristic of the two-way fixed and mobile services. Broadcast and data collection applications transmit only at one end and receive only at Me over end of We lick. The overall problem can be divided into two parts. The first deals with the satellite RF link which establishes communications between a transmitter and a receiver using the satellite as a repeater. In describing the satellite radio link, we quantify its capability in terms of the overaU available ca~Tier-to-noise ratio (C/N)A. This figure of merit, representing the ratio of the carrier power (the desired signal) to the noise power measured in a bandwidth, is directly related to the channel-carrying capability of Me satellite linlc. The value of (C/N)A depends on a variety of factors, which in turn depend on the available power and bandwidth for the earner. The second part of the problem concentrates on Me link between the earth terminal and Me user environment which, in most small systems, is incorporated into the user equipment. In the user environment customers are typically concerned with establishing voice, data, or video communications with either one-way or two-way connections. The quality of these ~`baseband', links is characterized by venous figures of merit such as transmission rates, error rate, signal-to- noise ratio, and other performance measures. For example, a data communications link used to transmit financial account balances must exhibit an extremely low rate of error to be effective. The error-rate specification for such a data communications service is directly translated into a required rate (C/N)Req per channel. The two parts of the problem can then be finked together when Me available (CIN)A of Me satellite link is compared to the required (C/N)Req dictated by the user application. The difference between the required (C/N)Req and the available (CIN)A is called Me link margin. Usually a link is designed to achieve a certain link margin, which is used as a buffer against occasional link degradations which are largely weaker related. The selection of ail appropriate link margin is highly dependent upon Me link's operating environment and its availability requirements. Availability is the percentage of Me time Mat Me link must operate LO\ NC~P 3-S! . Phi 2 Fin Report A1-261

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without a serv~ce-outage (typical availabilities range from 95% to better than 99.9% of the year). Intelsat fixed service offers an availability of 99.96%, unless redundant sites are used. The Satellite RF Link Ihe performance of a satellite link is typically specified in teens of its channel capacity. For this discussion, the following definitions are relevant. A channel is a one-way link from a transmuting earth station through the satellite to Me receiving earn station. A circuit is compnsed of two channels used for bi-dimctional communications between two earn stations. The capacity of a link is specified by We types and numbers of channels and the performance requirements of each channel. In practical terms, a voice service must provide circuits to its customers. The term "channel," however, may also apply to television and data circuits as well. For broadcast and data collection applications, one-way channels are typical. The channel-caIIying capacity of a satellite RF link is directly related to the overall available carner-to-noise ratio (C/N)A . Exclusive of interference, three basic elements are considered in designing this RF lick. The first is the uplink, representing the channel from Me transmitting earth station to Me satellite. The quality of this link is usually expressed in teens of Me uplink carrier-to-noise ratio (CINJu . The (C/N)U depends on the power of the transmitting each station, the gain of Me transmitting antenna, the gain of the receiving antenna, and Me satellite system noise temperature. The power of the transmitter on the ground depends on the size of the power amplifier employed. The gains of both the transmuting and receiving antennae are directly related to Heir sizes and efficiencies. The system noise temperature is a measure of Me degradation of the received signal caused by elements in Me receiver. This is composed of the receiver's amplifier noise the noise due to losses between Me antenna and Me amplifier, and Me antenna noise. \NCH]WhaS~\ NCHRP3-51 · PhaSe2Fina1RePOrt A1-263

The second element In Me RF link is the downlink. The corresponding figure of merit is caned the downlink caIrier-to-noise ratio (CM)D . Similar to We uplink, (C/N)D depends on Me power of the satellite transmitter, the gain of Me transmuting and receiving antennae, and Me earn station's system noise temperature. The third element to be considered in Me RF link design is Me satellite electronics system itself, which produces undesirable noise-like signals Mat are normally expressed in a caner-to-noise ratio which we can cad (~/N)I . Sever impairments, pnmarily intetmodulation effects caused by the non-linear operation of the satellite amplifiers, can be included In the (CHILI component. Interference from over satellites and terrestrial systems can also be coBec~vely characterized by a carner-to-~nterference ratio. one makes certain typical assumptions about He nature of Me noise-~ce impairments, then the three elements [(C/N)U (C/N)D and (CIN)I ~ can be easily combined to yield an overall camer- to-noise redo, (C/N)A . Due to the way this overall available camer-to-noise ratio (C/N)A is calculated, it can never be better Man Me worst of the three individual elements. Two basic components are required to establish a satellite link. The first is the satellite repeater, usually carded a transponder, and the second is a satellite earn station. The Satellite Transponder A satellite functions as a distant RF communications repeater which receives uplindc transmissions and provides fiItenug, amplification, processing, and frequency translation to the downlink band for retransmission. These sub-functions are briefly descnbed below. The typical transponder is a quasi-linear repeater amplifier, a block diagram of which is shown Figure A.~.7.2.2.2-2. The uplink and downlink bands are separated In frequency to permit simultaneous transmission and reception without self-interference. Moreover, Me lower- frequency band is normally used on the downJink to exploit the reduced atmospheric losses (at these lower frequencies), thereby minimizing satellite power amplifier requirements. Typical satellite transponder amplifiers must provide relatively large gains (amplifying Me signal power from 100 million to 10 billion times) while maintaining relatively low-noise operation. Channeliz~ng filters must be designed to minimize interference from adjacent channels, as well as [.WC~.~.Q,lK NCHRP3-51 ~ Ph~2~RePOrt A1-264

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other factors, including intersymbol interference and group-delay distortion. The final stages of amplification in the transponder are typically provided by traveling-wave tube amplifiers (TWTA), which tend to unintentionally distort He signals to some extent. ActuaRy, it is in this high-power amplifier stage Mat most of the impairments affecting (C - )I are generated. In multiple-carner operation, the unintentional Interaction between neighboring calTiers in the quasi-linear, high-power amplifier stage caned "intermodulation" is usually the dominant impairment. Adjacent channel and adjacent satellite interference must also be included in an overall consideration of impairments. These impairments are related to bow the design of He satellite hardware components and the design operating points In He RF link. ~ a satellite, the limitations on spacecraft mass and power, force systems engineers to balance the available power against the acceptable distortions due to non-linear impairments. One way to conserve power (at He expense of increased complexity on the satellite) is to use a regenerating transponder. ~ a regenerating transponder He digital signal is demodulated and demodulated within He transponder itself. This approach has die distinct advantage of separating the uplink and the downlink into two independent paws. Hence, neither of He links can degrade He performance of He other. The Earth Station The second basic component of a satellite link is an earn station. A block diagram of a typical earth station is shown in Figure A.~.7.2.2.2-3. Earth stations are available in a wide variety of sizes, functions, sophistication levels, and costs. They are categorized by function, by He size of He antenna, and by He level of radiated power. Antenna diameters range In size from as small as a simple whip antenna (on a hand-held terminal) to as large as 30 meters in diameter (for large international gateway stations). Larger stations may require tracking systems to maintain He pointing of the antenna at He satellite. This is because as He antenna increases in size, the width of the beam created by that antenna decreases and is thus more difficult to keep pointed at He satellite without tracking the sateBite's subtle movements. Smaller stations usually do not require tracking systems because of He large beamwidths of Heir (small) antennae compared to the beamwidths of He larger stations. L;`NC~Phasc2.'p`\ NCHRP3-51 · Phase2FmalReport A1-266

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An earn station consists of an antenna subsystem, a power amplifier subsystem, a low-noise receiver subsystem, and a ground communications equipment subsystem. Smaller earth stations (such as hand-held units or remote sensors) would have a self~ontained "ground communications equipment subsystem." The performance of an earn station is specified by its equivalent isotropic radiated power (EIRP) and its gain-to-system noise temperature ratio (G/T). ElRP is the product of the power output of He high-power amplifier at the antenna, and the gain of Be transmitting antenna. The receiving system sensitivity is specified by G/T, which is the ratio of Me receive gain of the antenna to the system noise temperature. The antenna gain is proportional to the square of He diameter and is dependent on the efficiency of He antenna's fee4Jreflector system. The system noise temperature is a measure of the degradation of the received signal caused by elements in He receiver. This is composed of He receiver's amplifier noise, He noise due to losses between the antenna and He amplifier, and the antenna noise). Although the performance of an earn station is typically limited by thermal noise, it can also be plagued with some of the same difficuldes caused by non-linear impairments in a satellite transponder. In general, the larger the station, the more affordable power levels and equipment become, and the fewer system design problems are encountered. The system designer must account for impairments such as intermodulation distortion in the high-power amplifier located in the earth stations as well as in the satellite transponder; however, He level of difficulty presented He designer In He earth station is less restrictive than that in the satellite transponder. The Terrestrial Link Referring again to Figure A.~.7.2.2.2-3, He second part of the end-to-end satellite communications problem is embedded in He link between the satellite earth station and the user environment. This part deals more specifically with the baseband signal (i.e. He signal before modulation or after demodulation). To provide adequate satellite service to a user, He service requirements must be well defined in terms of quality. Quality of service, specified in teens of parameters such as link availability, bit error rate, and signal-to-noise ratio, may Den be translated into a required caner-to-noise ratio (C/N)R in He RF link. The required camer-to- noise ratio (C~)R is then compared win the available canter-to-noise ratio (C/N)A to determine ~:\NC~Phase~rpr\ NCHRP3-51 · Phase2F~nalReport A1-268

He overall capacity of Me link. In designing systems to meet required quality and grades of service, several fundamental baseband processing elements must be considered. The first level of processing is source coding and/or baseband modulation, wherein a source signal (voice, data, or video) is processed into digital form or processed in analog form to prepare it for transmission. The most common forms of baseband analog processing are amplitude modulation (AM) and frequency modulation (FM). Either of these could be preceded by an analog compression scheme. Two typical forms of baseband digital processing are puIse- code modulation (PCM) and delta modulation (DM). Either of these could be followed by a distal compression scheme. Following individual channel coding, Be next processing level is often multiplexing (used when many channels are sent by a single user). For analog transmission, channels are often combined using frequency-division multiplexing (FDM). FDM employs separate frequency "slots" in a large analog carrier, each accommodating one channel. In digital transmission, multiple chatmels are often combined into higher-level digital signals using time-division multiplexing CORM). TDM employs separate time slots in a large digital canter, each time slot canying Me infonnabon for one channel. The next level of processing is channel coding, which may be used to improve the quality of digital transmissions by adding redundancy prior to transmission to reduce the overall error rate. Next, the process of RF modulation is used to modulate either single- or multi-channel signals onto radio frequency carriers high enough for transmission on the satellite link. Analog transmission typically uses FM and digital transmission usually employs some form of phase- shift keying (PSK). The final level in signal processing is multiple access. To exploit the satellite's geometric advantage, there must be a method which permits more Man one each station pair to use a transponder simultaneously. Multiple access techniques have been used extensively in satellite communications. The two types of multiple access techniques (FDMA and TDMA) have been employed for most commercial applications, while a Gird multiple access scheme (CDMA) has been used for mostly non-commercial applications. Sometimes combinations of these Tree ~\NCHRP~Phasc2~pt\ NCHRP 3-51 · Phase 2 final Report A1-269

multiple access techniques have been used to solve certain system-related problems. The three multiple access techniques are detailed below. Frequency Division Multiple Access The first multiple access technique is frequency division multiple access (PDMA), which employs multiple carriers within He same transponder, as shown in Figure A.~.7.2.2.2-4. It is the most common method in use because it was a natural extension of the FDM systems that were in use for many years in terrestnal canner systems. In FDMA, each uplink RF carrier occupies a defined frequency slot and is assigned a specific bandwidth in a multi-camer repeater. The receiving station selects Be desired camer by RF filtering. In PDMA, multiple access is achieved through frequency planning and coordination. The main disadvantage of using Me FDMA approach is that its multiple-carriers are vulnerable to degradations due to intermodulation in the transponder. T~me-di~sion Multiple Access The second multiple access technique is time-division multiple access (TDMA), which employs a single catner time-shared among many users, also shown in Figure A.1.7.2.2.2-4. It operates in "burst-mode," such that the transmission bursts from aH stations arrive at the satellite transponder consecutively. The bursts are contiguously interleaved without overlapping in time, also shown in Figure A.~.7.2.2.2-4. Each earn station receives all bursts from all stations (including its own) aIld selects those signals destined for its users. Using time-shared single- camer TDMA provides some distinct advantages over FDMA. In particular, a single-carrier TDMA approach avoids the intermodulabon distortion Hat must be accommodated In muld carner FDMA systems. u\NCHR~Phase~p~\ NCHRP3-51 · Phase2FinaIReport A1-270

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There are, however, two disadvantages to using the TDMA approach. First, it requires that all participating earn stations be coordinated to transmit Heir signals within Weir own, very precise, timing windows (typically only a fraction of a mid second in duration). Secondly, the transmit earn stations are required to have larger power amplifiers than Key might otherwise need to supply Heir brief transmission bursts win a relatively hefty pulse of power. On average, the power requirements for TDMA are He same as for FDMA (because they essentially use no power when it is not "their turn" to transmit a burst). But He larger amplifier requirement could significantly increase He cost of a small earn station. Code-div~sion Multiple Access The Hired kind of multiple access technique is known as code-div~sion multiple access (CDMA). This technique is one In which aB uplink signals occupy He same frequency band at the same time. Each signal has been "encoded" wad its own pseudorandom code which is chosen from an orthogonal set. In the receiver, these codes are used to extract He desired signal from the over signals. This system, also known as "spread-spectrum," has been used primarily in military applications for security purposes, but has been steadily gaining acceptance into certain commercial systems. Its advantages are that it can function in severe interference environments (which for other multiple access techniques would be impossible) and it can be used to spread out a signal's power so Hat it can avoid exceeding certain regulatory limits. The Tree main disadvantages to CDMA are that it requires precise power control at the transmitters (to avoid excessive interference between users); it requires complex processing in He receiver (to sort out the desired signal from the others); and its spread-spectrum nature can require more bandwidth per group of users than He over multiple access techniques. The foBow~ng sections offer descriptions of the venous aspects of a satellite system: orbits, satellite frequencies, channel bandwidths, typical digital bit-rates, and coverage capabilities. Orbits Most communications satellites are placed in a geosynchronous orbit which allows Rem to maintain a constant position in tile sky (see Figure A.~.7.2.2.3-~. Over communications c;`NCH~Phase:~p~\ NCHRP3-51 · Phase2FinalReport A1-272

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satellites are placed in non-geosynchronous orbits which causes their position to move across the sky (at speeds determined by Weir orbit height). This section looks at the benefits and problems associated with each type of orbit. The geosynchronous orbit offers a number of system advantages including simpler antenna pointing mechanisms for fixed installations, such as from a large broadcast center antenna, to a medium-sized TV receive-only antenna, or even a small remote sensor's antenna. By comparison, a fixed installation accessing non-geosynchronous satellites would require more complex satellite tracking hardware to keep the fixed insta~ation's antenna pointed at the satellite as it moves across the sky. In most cases, where an uninterrupted connection is desired, a second tracking antenna would be needed to begin tracking a new satellite as the current satellite drops below the horizon. Initially, it might seem that using a geosynchronous satellite that maintains a constant position in the sky would be less helpful for mobile-term~nal installations (like a car, truck, or trains, because the mobile urut's antenna would have to track the satellite anyway (because of its own movements); however, a mobile instigation would still be able to avoid the need for Hat second tracking antenna if it accessed a geosynchronous satellite instead of a non-geosynchronous satellite. It must be stated here that there is one simple way to avoid any complicated tracking antenna schemes (applicable to any fixed and mobile terminals which access a non-geosynchronous satellite). That is to use a terminal antenna with a very low-ga~n (and thus a very wide beam), which can "see" the entire sky at once and Bus receive and transmit to any satellite in the sky. This is the solution which has been chosen by many of Be up-com~ng hand-held sateBite-phone systems; however, this solution has some serious drawbacks, too. One drawback is that by reducing the antenna yarn one risks totally eliminating a broad class of potential services whose performance would depend upon an adequate terminal antenna gain. Another drawback is ~at, by using these very wide beam antennas, one has created a very significant interference problem, which usually results in significant reductions in Be amount of available bandurid~ (because Be available bandwidth may be divided, and sub-divided, into small non-overlapping segments and these segments must be used in a carefully coordinated manner). ~.`NCHRPPh~.~p'\ NCHRP3-51 · Phase2F~nalReport A1-274

Over system advantages of using the geosynchronous orbit include the maintenance of a simple continuous connection, without the complexity of having to periodically hand-off connections between non-geosynchronous satellites, and Me fact Mat they require only one satellite to provide national coverage, unlike the many satellites required for non-geosynchronous systems. One clear advantage of using non-geosynchronous satellites is that the path-loss is significantly decreased compared to the geosynchronous satellites because non-geosynchronous satellites are usually much closer to the earn (also shown in Figure A.~.7.2.2.3~. This reduced path-Ioss can result in improved margins, reduced transmit powers, or reduced antenna sizes. On the over hand, the closer a satellite's orbit is to the earn, Me faster it crosses an earth station's field of view. This faster crossing may make it more difficult to track these satellites and the periodic hand-off of connections between non-geosynchronous satellites win occur more often. For example, a satellite orbiting the earth at an altitude of 800 hen takes a maximum of about 15 minutes to cross the sky (from horizon to horizon), but a satellite orbiting the earth at an altitude of 10,000 km (about a third of the distance to the geosynchronous orbit) takes a maximum of about 130 minutes to cross the sky. Another possible advantage of using non-geosynchronous satellites (u ith mobile terminals) is that they can offer a better chance of having a good view of a satellite (assuming a random location for the terminals. This is because non-geosynchronous satellites can offer satellite diversity, which means that when the view to one satellite is blocked by a building or a mountain there is often another satellite in the sky which can still serve that terminal. Diversity is simply not possible for a single geosynchronous satellite; when it is blocked, service is impossible. One should also note Mat when non-geosynchronous satellites are totally blocked at one point in time, they can be relied on to eventually move to other locations Mat are unobstructed. The waiting- time (to get an unobstructed view) vanes significantly depending on local terrain and the specific orbital configuration of the non-geosynchronous satellites. Some configurations spend most of Weir time at lower elevation angles, while others are more likely to be found at more favorable elevation angles. The elevation angle to a satellite is simply Me angle measured up from Me horizon to the satellite. This "good-view" advantage of non-geosynchronous systems does not exist when considering mostfxed instaBabons, because Hey would not be installed where Hey have a poor view of the L;\NCHRP\Phasc2.rpti NCHRP3-51 · Phase2F~nalReport A1-275

geosynchronous satellite. The more significant question for geosynchronous satellite systems is, how difficult is it to find a good location? For most any location in a country such as the U.S.A. (which lies mostly above Me 30° N latitude line), We best positioned geosynchronous satellite can offer a maximum elevation angle of about 55° (which is restricted to the southern sky). Thus, Me only invalid locations are Nose which have their view to the soup obstructed beyond the 55° elevation angle by some obstacle. This seems to be a fairly limited case, and thus the chances of finding a good location for a fixed tenninal (using a geosynchronous satellite) are quite good. Satellite Frequencies There are advantages and disadvantages to using any of the various frequencies allocated to satellite communications. These differences are detailed in Table A.~.7.2.2.4-~. The table is ananged win Me lowest frequency band first, and successively higher frequency bands Hereafter. Note that the bandwidth available to He sateHite-mobile applications is significantly less Han that allocated to fixed-satellite applications. ~ addition, He sateHite-mobile bands ~ and S) are susceptible to multiparty fading (severe drops in signal power as He unit moves into a region of destructive signal self-~nterference) while He higher fixed-satehite bands (Ku, and Ka) become significantly degraded by rain losses. These degradations, along win He availability of affordable and reliable components, tend to make C-band frequencies He most desirable choice. Unfortunately, He available orbital locations and Bus He number of times He available C-band spectrum can be reused, are being consumed quickly. Thus, He frequency coordination and spectral utilization problems for He C-band frequencies have become severe. Therefore, He significant trend toward using higher frequencies continues, despite weir drawbacks. L.:\NCHRP\Phase2.sp`\ NCHRP 3-51 · Phase 2 primal Report A1-276

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At the upper frequency limit, the Ka-band frequencies are just starting to be used for commercial applications. These frequencies offer a significant reduction in interference problems (because very few satellites use them). They also offer a much wider bandw~d~, and they offer increased antenna gains for a specific antenna size, compared to lower frequencies. The main drawbacks are that they are susceptible to severe rain losses, they have a somewhat immature technology (and are thus more expensive and somewhat less reliable), and Heir increased paw loss cancels out the advantages of the increased antenna gains. The advantage of the sateDite-mobile frequencies Do- and S-band) is that Hey offer a reduced pa~-Ioss, which decreases with frequency, without being adversely affected by atmospheric scintiBadon, compared to lower frequencies such as Vim and UHF. These factors are important when considering the low-ga~n antennas which are typically used in mobile applications. (The low gains are compensated for by the reduced path-Iosses). The S-band frequencies have recently been added as mobile frequencies because the L-band frequencies were seen as insufficient for ad the near-term sateBite-mobile systems being developed worldwide. Channel bandwidths Channel bandw:~s are only constrained by the transponder bands, which vary considerably depending on desired frequency band and He specific satellite. A satellite could use one transmitter to handle He entire bandwidth (500 MHz at C-band), but modern satellites split He received spectrum into many individual transponders often having various transponder bandwidths within a satellite, see Figure A.~.7.2.2.~-~. Having a channelized repeater aids in intermodulation reduction by having fewer carriers per transponder. Some typical C-band transponder bandwidths are: 77 MHz, 72 MHz, 54 MHz, 41 MHz, and 36 My. Some typical Ku-band transponder bandwidths are: ~12 MHz, 77 MHz, 72 MHz, 54 MHz, and 27 Adz. Typical L-band transponder bandwidths are: ~ MHz and 30 MHz. The 30 MHz L-band transponders are usually channelized into many small (about ~ MHz) bands to achieve He complex channelization plan required to access He discontinuous spectrum available at L-band. c:`NCHRP`Phasc2aprx NCHRP3-51 · Phase2F~nalReport A1-278

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Typical digital bit rates There is a very broad wage of digital bit rates being used on satellites today. Examples of Me range of digital bit rates are detailed in Table A.~.7.2.2.6-~. The table is arranged win We lowest bit rate first, followed by successively higher bit rates. Note Tat the transmission of digital data can be performed by a custom-designed, application-specific digital canter or by some standardized digital carrier system (such as Me T! system). Table A.~.7.2.2.6~1 Typical Bit Rates for Digital Satellite Communications . . Bit Rate | Example Applications . ~ 100 bit / s . Satellite paging services 300 bit / s Low-rate mobile data terminal .4 to 9.6 knit/ ~. ~w ~= ~ ~ 56 to 128 kbit / s Digitally compressed (CD quality) audio . .._ Hierarchical Digital Data Transmission Formats: T1: 1 .544 Mbit / s T1 (capacity: 24 digital voice channels) T2: 6.312 Mbit / s T2 (capacity: four T1 carriers) T3: 44.736 Mbit / s T3 (capacity: seven T2 carriers) 5 to 15 Mbit / s | Digitally Compressed Video 155 Mbit / s Broadband-lSDN Applications The bandwidth for compressed video transmissions depends largely on the image quality requirements of the application and the information content of the unage. For example, a reporter on a news show or a shopping network program has a low information content because there is little change from one picture to Me next, so a compressed video transmission at 5 Mbit/s would deliver a high-quality picture. While a fast moving basketball game or music video has a high information content, and would require a compressed video transmission at around 15 Mbit/s (for a high~uality picture). At the upper extreme of digital satellite bit rates is a 155 Mbit/s system developed for Broadband-ISDN applications. This system is capable of offering 140 Mbit/s fiber optic cable restoration services through a single 72 MHz transponder. t.:~NCHRP\Phascz.rp~\ NC~P3-51 · Phase2F'nalReport A1-280

Coverage capabilities There are four basic types of satellite coverages: global coverage, regional coverage, spot beam coverage, and what could be caned "ceBular-beam" coverage. Some combination of these is often used on a single satellite. AgZobal coverage beam is one Mat can cover We maximum amount of Earth's surface from Me sateDite's point of view. A global beam on a geosynchronous satellite can cover about 42~o of Earth's surface (see Figure A.~.7.2.2.5-~), while the coverage of a "global" beam on a non- geosynchronous satellite vanes in proportion to its altitude (but is always less Man a geosynchronous global beam's coverage). These beams offer less gain Man the other coverage options and tend to be banduid~ inefficient (because Weir frequencies cannot be re-used). They should only be considered when a very large (seamless) coverage region is required. A regional coverage beam is one which is shaped to provide coverage to a specific region. These beams are more power efficient than Me global beams because Hey provide power only in the region where it is needed and they are less likely to cause interference for the same reason. These beams range in size from a hem-beam (which covers approximately half of the global beam coverage), smaller zone-beams (which cover about a quarter of the global beam coverage), and national coverage beams (which can usually cover a country of any size with one beam, see Figure A.~.7.2.2.7~. Somet~mes these regional beams are supplemented win small spot beams to include discontinuous regions (like Hawan) without wasting power on the area between these regions. A spot coverage bean can provide a small region with a very powerful signal, but usually several beams are needed to achieve some sort of reasonable coverage (see Figure A.~.7.2.2.7-2~. Each beam must have its own signal paw since beams cannot share amplifiers if Hey are to remain independent spot beams. When spot-to-spot connections are desired (i.e., for mobile systems, which need these high-ga~n beams), the mute of possible interconnections between these spots becomes a major difficulty in satellite design. Often the solution to this interconnection problem is Hat each spot is fed into a single "feeder-link" connection, which communicates why a central hub earth station, which means Hat spot-to-spot connections must be sent through the hub. This is known as a "double-hop" connection. A 'Yeeder-link" connects the satellite to a u`NCHRP - a=.,p`` NCHRP3-51 · Phase2FmalReport A1-28 1

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central hub earn station which both supplies the satellite with signals to be distributed among its downlink beams and receives signals collects by the uplink beams. ~ only one '~feeder link" is used, then all of Me sateDite's signals must pass through this link. The "cellular-beam" coverage can be thought of as a combination of global coverage and spot- beam coverage (essentially the entire field-of-view of the satellite is covered by spot beams). This offers the advantage of having the whole region covered, but with high gain spots, instead of the single, lower gain, global beam. This configuration is typically used for hand-held satellite mobile phone systems, now being developed. Again, We massive number of interconnections between these spots are usually solved by connecting each spot to a single feeder link connection, which then handles He spot-to-spot connections via He hub. Some systems solve He connection problem by demodulating all the incoming signals, re-routing them to the proper beams (in their digital form), and then remoduladng Rem before transmitting them. This scheme offers some distinct advantages such as breaking He uplink from He downlink, which improves performance, and offering complete connection flexibility. But its complexity is still quite ambitious for a satellite-based process. A.~.7.2.3 Types of Sate//ite Services There are many vaned uses of satellites in today's world. Orig~naBy, commercial satellites were used for two purposes: 1) To transmit television signals between major broadcast centers around He world, and 2) To transmit phone conversations around He world. Since Lose early days, He range of applications has greatly expanded. Today it includes: . Very-Smal1 Aperture Terminals (VSATs) · ~ ~nd-mobile communication systems Video/Satellite News Gathering (SNG) applications Network television broadcast distributions Satellite distribution of newspapers Vehicle tracking services SCADA (Supervisory, Control, And Data Acquisition) services · Private telephone/data networks Cable-programming distributions L;`NCHRP^a~.rp`\ NCHRP3-51 · Pbase2FmalReport Al-284

Distance-learn~ng systems Manne-mobile communication systems In-fli~t phone service Cable restoration services Direct-broadcast TV services National satellite paging systems Satellite imaging of Be earth Satellite weaker services · Direct audio broadcasting services · Leased or on-demand satellite capacity. These applications will be discussed in Be following paragraphs. (All of the systems typically use the C-band and Ku-band (fixed-service) satellite frequencies, except where noted.) VSATs The ubiquitous VSAT installations which we see on a growing number of roofs (mostly gas stations and retail stores), allow the users to validate credit-card and debit-card transactions as wed as per~odicaRy transfer the sales information to some central data collection entity. The user equipment consists of He small diameter (aperture) antenna and a small box containing Be terminal electronics (data interfaces, encoders/decoders, modulators/demodulators, multi-access protocol managers, amplifiers, filters, etch. This box is typically interfaced to the user's computer equipment and accessed via those computers. Land-mobile communication systems Current systems operate wad L-band frequencies and offer a wide range of services in this area. From portable (suitcase-sized) terminals which can be set-up In a few minutes, Epically used for military or remote news-repordng applications, to smalder vehicle mounted terminals, which provide mobile voice, fax, and data connections in regions without cellular-phone coverage. Win future systems (around Be year 2000) offering hand-held, global, phone communications. Video/SNG applications Often these systems are responsible for the video news footage from '~ot-spots" around Be world which are often in regions having inadequate communications infrastructures, such as sites I.:`NCHRP`Phasc2.'p'` NCHRP3-51 · Phase2Fi~Report A1-285

of air disasters, natural disasters, war-torn regions, impoverished regions, etc. This technology is also used by news crews to provide live "on-~e-scene" reports of local and national events. Network television broadcast distributions TV networks use satellites to distribute Weir programs to the local network affiliate stations who then broadcast the shows according to their own particular schedules. Typically these "network feeds," which have blank segments for local commercial insertions, are transmitted in an encrypted form to prevent unintended reception of the signals. Satellite distribution of newspapers In order to provide nationwide distnbudon of certain newspapers without the delay and added cost of transporting them over long distances, the practice of transmitting the newspaper electronically via satellite has been adopted. These signals are then received by many local newspaper printing plants which print out the final product for local delivery. Vehicle tracking services These could be divided into two distinct services. In Me first type, Be user can interact with the terminal to send/receive messages to a central location. (One such system is in-use in Be long- hau} trucking industry and more are about to be deployed.) The second service is unattended vehicle tracking in which a small unit automatically gives position updates to a central location via satellite. Currently, this satellite service is offered in a somewhat ad hoc manner by a few companies, but several sateHite-based systems are in venous stages of offering a complete programs of this much-sought-after service. SCADA This satellite service has been around for many years. It is used for venous remote data collection and control applications, such as environmental monitonng, pipeline monitoring, and other control/mon~tonng activities. This application can also use a non-stationary satellite system in which a satellite regularly appears in He sky above He remote unit aIld signals it to dump its data into the sateDite's store-and-forward data barks. L:~h~.~\ Net 3-51 · Pee 2 Fit Reed A1-286

Private telephone/data networks These systems are used by businesses which require a dedicated network for Weir data transmissions and phone communications. Typically, the need arises when the amount of traffic (telephone and/or data) is so large Hat using a dedicated network is more cost-efficient than using Be public telephone network and/or some public data network. This application usually consists of a small to medium sized dedicated network for each site and a leased segment of a satellitets capacity with bow earth station size and leased segment bandwidth depending on Me desired peak traffic. This satellite-based network configuration can make adding an additional site much easier Ran a "w~red-in" service, especially for remote sites. Cable-progr~mming distributions Cable-programming suppliers use satellites to distnbute Heir programs to He local cable companies (and others) who then incorporate this programming with over satellite and broadcast feeds. Typically these cable-programm~ng distributions are transmitted in an encrypted form to prevent unintended reception of the signals. Distance-learning systems Some universities and schools have two-way TV circuits between a central location and some remote learning centerks) to increase the educational opportunities available to people in these remote locations. These systems require the w~de-bandw~dths and complex connectiv~ties that only satellites can offer. Marine-mobile communication systems Before satellites, marine communications was chiefly conducted via high-frequency (Em) radio, whose erratic performance could be Iife-~reaten~ng in emergency situations. Current satellite systems operate with L`-band frequencies and offer a wide range of services in this area They range from medium-sized, ship-mounted tenninals which can provide voice, fax, and data connections to fairly-small low data-rate terminals which can communicate telex-style. The larger terminals are typically used for larger commercial vessels and phone communications aboard cruise lines, while the smaller terminals are typically used for smaller commercial vessels and noncommercial vessels. Future global systems (around He year 2000) may offer hand-held phones for bow land and sea comrnun~cations. L;\NCHRP`Phase2.rp~\ NCHRP 3-51 · Phase 2 Fmal Report A1-287

-flight phone service Cu~Tent in-flight satellite-phone systems offer various levels of services for a traveler aboard a commercial jet. Some systems offer just a few phone kiosks for all Me passengers to use (only for out-going cars). But, the more advanced forms of this service allow travelers to place or receive phone calls from the comfort of their seats. Future systems may offer improvements in the data-rates available, along with other features. Current systems operate with L-band . frequencies. Cable restoration sernces Under-sea cables (either copper or fiber-op~c) tend to break once in a while. Satellites are often asked to serve as a temporary pathway for data and voice traffic while the cable is being repaired. Direct-broadcast television services This idea has been around for quite some time but until recently the equipment costs were seen as unreasonable to all but the sateBite-v~deo hobbyist. Win the advent of digital video compression schemes, a new system has emerged which offers hunches of channels of high- quaiity video to Me end-user, win hardware costs much more in line with consumer expectations. This significant change in the fortunes of direct-broadcast television services is very illustrative of how a modest improvement in a cntical design element (in this case the required channel bandwidth and powers can transfonn a service/system which was unfeasible into something very desirable. Nadonal satellite paging system These fairly new systems are a logical extension of He more traditional pagers which can only operate within the transmission limits of the local paging company or perhaps in several local markets if "roaming" agreements are effected. The satellite paging systems can deliver a paging message to anyone anywhere within view of the satellite, easily covering an entire country. Satellite imaging of Earth itiaBy, this technology was developed so that spy satellites could safely monitor another nation's activities. It has since expanded to provide scientific, environmental, and commercial L;`NCH~Phase2~p ~NCHRP3-51 · Phase2FmalReport A1-288

data on land use, the oceans, and many over human and/or natural phenomena The use of satellite imagery for such applications has been a steadily growing industry for many years. Satellite weather services Another, more familiar, use of satellite imaging technology is weaver prediction from He analysis of atmospheric images and other data A logical extension of this capability would be to deliver this information directly to the Raveler. Direct audio broadcasting (DAB) services Many DAB systems are currently being developed, in a race to deliver CD quality audio via satellite. Most of the systems are based on direct delivery to Be consumer via satellite, or delivery to a cable system which would then caTTy Be service to Be consumer. The stated goal of these systems is to offer many channels of him quality digital audio at reasonable prices. Note that the systems use venous different digital audio compression schemes, usualRy of a proprietary nature. Leased or on-demand satellite capacitor These terms describe Be two basic ways in which bulk satellite capacity can be obtained from venous satellite operators. By leasing satellite capacity (typically a full transponder for a year or more) the transponder can be used for whatever traffic (voice, data, video) is desired, at any time, and any loading factor. The user might even sub-lease portions of the transponder, or certain daily time-sIots. Leasing is generally the cheapest way to obtain sateldite capacity on a per minute basis, but if a user's traffic demands are infrequent, Men a more practical approach would be to arrange for on~emaIld satellite capacity. With on-demand capacity, users only pay for what they use, but per minute charges are significantly higher than lease rates. In addidon, wig on-demand capacity, Be user must arrange for Be capacity to be made available, and Mere is some chance ~at, in extreme loading situations, capacity may not be available when needed. A.~.7.2.4 Types of Termina/Equipmenf There are several distinct types of satellite terminal equipment, Be characteristics of which are usually dependent upon operating environment and capacity. These types can usually be divided into Free classes: mobile, transportable, and fixed. LUNCH - Phasc:.rp`` NCHRP3-51 · Phase2FinalReport A1-289

Mobile terminals Range from hand-held satellite phones to vehicle-mounted satellite mobile terminals for automobiles, trains, ships, and airplanes. They all must be able to deal win the signal degradations introduced by their own movements. These degradations include Doppler frequency shifts (changes in the carrier frequency due to the relative movement between He transmitter and receiver) and multipath fading (severe drops in signal power as the unit moves into a region of destructive self-~nterference). The hand-held satellite phones are battery powered and thus, to prolong the time between recharges, have extremely low-power transmitters. They also have very low-ga~n antennas which are relatively inexpensive and, more importantly, can "see" the satellite regardless of the user's orientation, unless the path is blocked by a obstacle. The configuration of vehicle-mounted satellite mobile communications terminals vanes depending on the intended vehicle and channel capacity. Communications units generally use a hi~er-gain antenna than hand-held units and ~us, they must be capable of maintaining proper antenna pointing while the vehicle is moving. Units which provide multichannel telephone capacity for oceanliners can afford to have a fairly large antenna (mounted somewhere away from the public), while the terminals providing similar service on airplanes must use conformal arrays of antennae that add minima drag to the aircraft. The antennae for train-mounted terminals are not as height-restncted as for aircraft, but Key must be able to fit through a tunnel. Automobile-mounted terminals need only carry a single channel, but Hey must be fairly low- profile, wig a very good antenna tracking capability (because automobile tums are fairly rapid), and Hey must have reasonably low price tags. Vehicle tracking/data terminals are another class of satellite mobile terminals. These units usually have a very low data rate, may have a self-contained power source (for secunty), and often have a very low-ga~n antenna, which is relatively inexpensive and can "see" He satellite regardless of the terminal orientation. L;~NCHRP`Phase2.rp~\ NCHRP3-51 · Phase2FmalReport A1-290

Transportable terminals Range from systems which can be canted in a briefcase, to those which require a couple of large suitcases for transportation, and those which are mounted on the back of a truck. All of these systems require some sort of set-up procedure once they have reached weir intended location. Typically, Hey cannot be operated while in motion. The briefcase and suitcase transported systems are usually just portable versions of He previously mentioned vehicle-mounted terminals. The truck-transported systems are usually just mobilized versions of fixed earth stations; most are transportable SNG terminals. These systems require some portable power source from batteries to diesel generators, and they usually include aB the terminal electronics necessary for stand-alone operation. For the transportable SNG terminals, this usually includes all the equipment needed for a bare-bones television studio. Faced terminals Range from small SCADA tennis (used for venous remote data collection and control applications), to VSATs and huge international gateways (for telephone, data, and television transmission). The SCADA terminals can vary significantly depending on their specific dudes, but they are usually small self-contained units which transmit or receive data in infrequent bursts to conserve battery power, and have venous sensors feeding them data The charge on He batteries is very likely to be maintained using solar-elec~ic cells. If the SCADA terminal communicates web a non-geosynchronous satellite, then it is likely to use low-ga~n antennae which can "see" He satellite regardless of where it is in He sky. VSAT terminals use a small diameter (less Man a meter) antenna which may actively track He satellite, depending on the satellite and He terminal's beamwid~. They are typically powered] by standard AC power. Their terminal electronics (data interfaces, encoders, decoders, modulators, demodulators, multi-access protocol managers, amplifiers, filters, etc.) are typically interfaced to He user's computer equipment and accessed via Lose computers. The larger terminals, including He huge international gateways twin antenna diameters up to 30 meters), can be Nought of as larger forms of He VSAT terminal. Most of He differences are related to volume, type, and cnbcality of Heir traffic. The larger earn stations require a much L;\NCHRP\Phase:.lp~` NCHRP 3-51 · Phase 2 Fmal Report A1-291

more stringent approval process, significant site construction, stand-by diesel power generators, and a full-time maintenance crew, because they cannot be idled by problems. A.1.7.2.S Planning, Design, Installation, Operation, end Related Costs This section presents the planning, design, installation, operation, and related cost issues for a potential satellite-based communications solution, which could serve a broad range of ITS needs. The solution is based on the ubiquitous VSAT terminal, which is a good example of a complete satellite network solution, with remote units and a hub unit. An example of an altemadve solution is one Hat is based on an Inmarsat terminal, which offers the connectivity of a complete network without the necessity of own~ng/operat~ng the hub unit (which can be quite expensive). The strengths of the VSAT system are Cat it is reliable, flexible, proven and offers significant cost savings, compared to terrestrial systems. VSAT systems are independent data networks, which offer additional facilities (such as voice and one-way videos and Key are offered by single source suppliers, to achieve one-stop shopping. VSATs are widely used in various industry sectors, such as: · Automotive · Financial · Government · Manufacturer/distributor All automobile manufacturers and dealerships or companies running services for this sector. Including banks, stock exchanges, brokerage houses, financial information, dealership companies, and insurance companies. Such as police, fire service, foreign ministries, education, and disaster monitonug and management. All types of manufacturing, excluding companies overwise addressed such as automotive. Distributors include trucking delivery and courier companies. ~:WC~P`Phase2~p`\ NCHRP 3-51 · Phase 2 animal Report A1-292

l user Retail fonnation Travel Typically He SCADA marketplace, but also gas stations and refineries, power generation plants, gas and water suppliers, and control installations. All types, regardless of merchandise. Includes supermarkets, fast food restaurants, department and hardware stores, etc. A general category which includes software companies, lottery systems, press agencies, newspapers, television and radio stations, and Be media generally. Includes any company related to travel such as airlines, travel agents, rental car firms, and hotels. Typically, users in this sector will be primarily concerned win reservations systems. Over Me years many new users and operators of VSATs have gone through He process of business planning, system selection, licensing, marketing, sales, and various over operational aspects of establishing a shared hub VSAT business or private network. Some of the major issues which a potential purchaser of a VSAT system should consider are: r. . `lcens~ng · Operating License . Nabonal/international - · Voice, data or video . interconnection (one end of the circuit or Trough He national signatory) Frequency License . Costs · Hub Frequency coordination RFI (hub antenna) · VSATs L~:\NCHRP`Phase2.rp'` NC~P3-51 · Phase2~malReport Al-293

· Software Standard software Network Management System (NMS) Protocols Spares (lead time, spares pool location) Additional test equipment (typically 30 percent of overall hardware cost) Space Segment · Availabilitv Costs Coverage Expansion Access charges and procedure Financial and Business Planning Compan son with over technologies or services Roll-out . Critical assumptions Speed of roB-out Implementation versus biding (usually a substantial delay between Me two) Lease or purchase (of clean btle) · Staffing · Other running costs · Utilities (electricity can be a large component) · Trials and pilot networks (staff resources, datacomms expertise) Basic equipment funding requirements · Marketing · Sales J Procurement Process · Technology · Price (always undergo a compete tender if possible) · Equipment reliability (comparable reference customers) ~ Oh.\ NCH" 3-51 · Pee 2 Fee Reed A1-294

/ After sales support (should be part of He contract conditions) · Technical · Sales/marketing Software support (annual maintenance or one-off purchase) Delivery/lead times (penalty payments in case of late delivery) Technology . Network topology (star, mesh, or hybrid) · Frequency and associated costs Access scheme as TDMA a requirement or does SCPC offer a better solution?) Customer applications in He market to be served Upgradability ~nroute/outroute configuration: How does the system hub expand?) Software reliability · Support for additional features . Voice/facsimile · LAN Obsolescence (Has He manufacturer kept backwards compatibility?) SkiR Set Requirements Staffing and recruitment · Training implementation Site preparation Zoning/plann~ng permission Power, etc. (Will He site require an un~nterruptable power supply?) Future requirements Other current VSAT technologies One-way systems: · Data . Digital/analog audio · Video L:\NCHRP\Phasc2arptN NCHRP3-51 · Phase2FmalReport A1-295

SCPC /point-to-point Mesh systems ~ Voice · Data (At whet rate? Protocolsupport.) · Overlay systems (making use of an ex~sdug SCPC network) Backhau] (impact on network availability) Over Services · Microwave · Fiber The issues of voice and video capability, installation, service, maintenance, system upgrades, spares, technical support, network management, and financial aspects of He VSAT system are discussed in Me following sections. Voice Capability Und] acceptable low coding rates were available, voice was always a sticky issue, because any system can run it, but whether or not it is a practical implementation is something quite different. Voice channels are effectively continuous and this type of traffic does not sit well in a packetized transmission environment designed to handle short-burst traffic. Video Video services currency remain tied to one-way analog broadcasts on interactive VSATs. Most systems support video and only require Me relatively minor addition of a receiver at Me remote site. At one time it was Fought that video broadcasts for training, ~n-store advertisements, product announcements, and central management pronouncements would be a major driving force for potential VSAT sales. Installadon Instadadon of a VSAT system appears to be one of Dose events which can take forever. In the beginning of Me VSAT industry it was quickly discovered by many landlords Mat Weir roofs had value. This is a cynical statement because many companies and individuals were concerned about Me potential damage Mat the erection of a 1.8 meter antenna could do to Me fabric of Weir buildings. Nevertheless, Me negotiations of roof rights soon became a major talking point and L;`NCHaP`Phase2.rp`\ ~CHRP3-5~ . Phase2Fn~3Repor' A1-296

there were numerous grumbles about just how much was being asked by owners for the privilege of installing a dish, which, after all, was "very small." Despite ~is, zoning or planning permission is an issue in all parts of Europe and has definitely slowed Me deployment of many networks. ~ addidon, the instaBadon process, which includes site survey and license application, becomes more complex and more expensive. Generally, only Dose involved win antennae In some way realize We enonnous differences between a I.2, I.8, and 2.4 meter dish diameter, i.e., each small increment actually represents a doubling in overall size and is very noticeable when viewed in reality. One point often suggested is ~at, by and large, a 1.~-meter dish can fit into a good elevator whereas a 2.4-meter one win not. If this is ever the case, the difference in He cost of installation may be huge if a crane is required to get He larger antenna into position. The move is toward antennae with a diameter of less Han a meter making installation of a VSAT far easier. Still, cIatms that, with this size, ~nstaBabon can be accomplished by one person rawer Han a two-man team are questionable, since somebody has to pull the other end of He cable, so two people are required regardless. Service and maintenance Service and maintenance of the network following its installation is usually handed by a national organization. There are two points of concern, software and hardware. Software issues are addressed in the following section along wad concerns about system spares. It is probably worm noting at this point that VSAT remote terminals, both one-way and interactive, have proved to be extremely reliable. Most manufacturers claim M~3F1 rates of 100,000 hours or morel and, despite He fact that these claims are based on calculated rates, operators all over He world inform us that reliability of the equipment is not a cause of concern for ~em, because the systems can be broken down into a few basic sub-systems: the indoor unit aDU), the cabling, the outdoor unit (ODU), and He antenna. Components inside these units cannot, in general, be repaired in the field. For this reason, in the event of a failure, the fault will ' MTBF - Mean T~me Between Failures. 2 1OO,OOO hours equals almost 1 ii/2 years, longer than He VSAT industry has been in existence. L;\NCHRP\Pbase2.'p~\ NCHRP3-51 · Phase2PinalReport A1-297

be traced to a sub-system and this entire unit removed and replaced, while the faulty unit is returned to the factory for repair. Most users contract for a VSAT network at least partly because of its reliability in comparison to the terrestrial alternative. It therefore follows that, in He event of a failure, Hey wiB require a speedy response. Typically, a response time of two to four hours is offered by service providers in Norm Amenca and Europe. One problem which some operators have encountered has been service-cars for network failures which actually originate in He customer's own equipment. System Upgrades and Spares Typically, customers may either pay an annual software maintenance fee and receive any upgrades to He system software during He year, or Hey may purchase new releases as and when Hey decide to. Another question of relevance is Hat of hardware spares. In He United States, several vendors maintain their own spares pools located in various places around He country; however, some manufacturers are known to have demanded Hat private hub customers purchase and maintain Heir own spares pool. Technical Support Tra~n~ng of hub staff usually takes place at He manufacturers' own hub and is organized in two to three-week sessions. Most manufacturers maintain a hub almost exclusively dedicated to new customers, product Dials, and staff training. Costs vary, but we believe that a charge of between $15,000 and $20,000 per person for a two-week session is typical (accommodation and meals not included.) In addition, 'hotline" support from the new hub to the manufacturer's own network operations center is part of the standard package. Network Management All of the major manufacturers offer a modern network management system. On the face of it, all of the systems primanly offer a "user friendly" graphical interface which certainly appears far more attractive than the old text-based screens; however, each NMS has its own strengths and weaknesses and He new, for He most part windows-based systems, are serious products which also bring a great deal more functionality to the user. Almost all of He systems are based on L::U<CHRP\Phasc2.rpr\ NCHRP 3-51 · Phase 2 Filial Report A1-298

workstation or PC computing platforms and thus, most support some form of remote network management monitoring and control. Each EMS offers He user a much higher degree of customization wad respect to default views of Be network, structured menus, alarms, and alerts. Some even offer diagnostics and spectrum analysis which would overwise have to be acquired elsewhere. Financial Aspects The financial aspects of a VSAT system should, in theory, be relatively straightforward, and in many instances, no doubt they are; however, from a worldwide view of overall deals, the combination of remote terminal and hub hardware, software, service, maintenance, and space segment can lead to enormous differences in price from region to region and even between countries in the same region. Price of systems can also be tied to over less obvious issues. Some composes choose their systems on We basis of past relationships or over business deals rawer than He merits and costs of He systems themselves. For example, a VSAT license in a country may be tied to bids from local companies for a contract with the licenser. These local companies first enter a round of "beauty contests" web the VSAT system manufacturers, Hey then choose a system and bid to the licenser. Thus, it might not be the best or the cheapest system which wins out in that particular instance, but rawer He manufacturer who backed He most likely winner of the licensing contest. The prices for individual components vary tremendously, region by region, but broadly, the figures which some companies have paid over He past few years are listed in Table A.~.7.2.5-~. These numbers illustrate He fairly expensive nature of the VSAT hub (from $120,000 to $2,500,000~. This encourages potential users to look for over options in this area, such as sharing the hub (which happens more than 30% of the time, as seen in Figure A.~.7.2.5-~), or contracting win a company that supplies He hub service. As mentioned previously, a service- supplier such as ~marsat would be able to offer such an alternative solution Coffering He connectivity of a complete network without having to own/operate the hub units. Table A.~.7.2.5-2 shows the significant features of He many Inmarsat standards along win typical access charges. These rates can be traded off against the reduced rates of a private VSAT system, whose initial hub costs, along win He associated costs of service aIld maintenance, must be considered. L;\.NCHRP`Pha~.~p~\ NCHRP 3-51 · Phase 2 Fmal Report A1-299 l

Table A.~.7.2.5-1 VSAT System Component Pricing Examples I . 1 . . Hardware (including R :) Low Average K`, - band Mini VSAT $4,500 $6,000 Ku - band Full VSAT $7,000 $8,500 C-band Full VSAT $10,500 $14,500 Ku - band Hub $500,000 $750,000 Ku-band MiniHub | $120,000 1 $250,000 C-band Hub $900,000 $1,500,000 . . _ Additional Hardware Low Average VideoNSAT $1,000 LAN CardNSAT $1,500 $1,700 Voice CarWSAT $1,500 $2,000 Non-penetrating Mount $850 $1,300 Software Low | Average User Network Protocol $8,000 $12,500 Network Management System $50,000 $100,000 Software Maintenance Release $100,000 High $7,500 $10,500 $36,000 $1,500,000 . 1 $500,000 $2,500,000 -- 1 High $2,000 $4,000 $2,000 High $50,000 ~ _ $200,000 1 1  L:\NCH~Phasc2.rpt\ NCHRP3-51 · Phase2FmalReport A1-300

l o o CL a' ~ · - - Q co 1~  O a) \ m B' _ ~ _ m In me ~ ' Cat At: C, :c ~ to ~ to to to c. at: m

Table A.~.7.2.5~2 Characteristics of Various tnmarsat Terminals Features Inm.A Inm-B Inm-C Inm-M Mini-M Channels ~1 ~ ~ ~ ~ ~ ~ ~ Voice ~Analog ~ 16 kbit / s ~ 6.4 kbit / s | 4.8 kbit / s Basic Data ~9.6 kbit/ ~ 9.6 kbit/s ~300 bit/s ~ 1.2 kbit/s ~ 1.2 kbit/s Max Data ~ 64 kbit /s ~ 64 kbit /s ~600 bit /s ~ 2.4 kbit /s ~ 1.2 kb~t /s RFBW T 40kHz | 20kHz | 5kH~ 10kHz | 5kHz Access | FDMA/SC C | FDMA/SCP | FDMA/SCP FDMA/SCP | FDMAISCP Mod FM Offset-QPSK Offset-Q PSK Offset-QPSK Offset-QPSK Type Continuous Burst Burst Burst Burst , HPA 1 40W T 20W I 16W 20W T 4W Talk Time N/A N/A NIA 20 mins. 1.5 furs. Band ~T ~ ~ T ~ $/min. ~ $9/min ~$7Imin. ~N/A $5/min. ~ $2-$3/min. References Morgan, W.~. and G.D. Gordon, Communications Satellite Handbook, Wiley-Interscience Publication, New York, 1989. Pritchard, W.~. and I.A. Sciulli, Satellite Communication Systems Engineering, Prenbce-Hall, Inc., Englewood Cliffs, NI, 1986. l L.\NCHRP\Phase2-rptY NCHRP3-51 · Phase2FinalReport A1-302

A.~.7.3 Broadcast Suboarriers for ITS (Ihis section is repented from Broadcast Subcarriers for ITS: An Introduction, by Eric Small, win permission of the publisher. Complete book available from: Modulation Sciences, Inc., 12A World's Fair Dnve, Somerset, NJ 08873 USA.) Abstract Lack of radio frequency spectrum specifically allocated to ITS applications poses a serious constraint to the timely introduction of new systems. Many key ITS projects require a significant number of communications channels allocated on a national basis. The FCC rule making procedure for providing radio spectrum to new services is, by design, a slow and cumbersome process. It is not unusual for a rule making proceeding to take ten years. Subcaniers on FM, TV aura] and AM radio broadcast stations offer an immediate solution to the need for digital and analog communications channels from infrastructure to vehicle. Subcarners also have the capacity to serve a portion of ITS communications needs well into He future. This paper compares the communications capacity of venous broadcast subcamers from an lids prospective. These include bow existing systems such as RIDS, SAP, PRO and venous proprietary schemes, as well as some of the recently proposed systems. No specific technology or system is advocated. Significant practical considerations that arise in using subcamer channels in the context of Norm American broadcasting are also explored. The Need InteBigent Transportation System applications share an alTnost universal need for radio channels. The requirement to communicate voice or data from the infras~ucture~ to Me vehicle is essential to most plans for ITS. Radio spectrum, especially Nose frequencies suitable for land-mobile use, is a scarce and valuable resource. Although 11 S deserves spectrum more Man most others competing for channels2, Me process of allocating spectrum to a new service remains slow and complex. The L:~h~.~\ NCH"3-51 ~ P~2F~Re~n A1-303

FCC rule making procedure can take ten years, and if litigation results (as it likely will, given He adversarial nature of He rule making process), it could add years more to He process. An additional pressure win be the almost certain explosive grown of ITS as it deploys. If grown in demand for ITS services becomes exponential (a likely situation), allocated spectrum will lag far behind the need for many years. This is a nonnal state for a scarce resource faced win a rapidly growing demand. How then can ITS grow without being hampered by a shortage of radio spectrum? Broadcast subcarTiers, sometimes Incorrectly caned "SCA3," offer a viable solution to bow the immediate needs of ITS demonstration projects, as weB as He long term requirements of an operational system. Broadcast subcarners can provide audio or data transmission channels for almost any ITS application. The range of reliable coverage is excellent, as great as a 40 mile radius for some radio and TV stations. The number of potential channels available is vast~ypicaRy two channels on every FM radio station in the country and at least one for every TV station. Why Broadcast Subearriers? Subcamers on either FM or TV broadcast stations represent a significant option to deploy ITS without being restrained by lack of radio spectrum. The following are some of the features of broadcast subcarners: Broadcast subearr~ers are available right now. Ah Hat it takes is an agreement between the ITS service and a radio or TV station. No regulatory approval is required from any government agency. Sub=~iers are a mature technology. Background music services such as MUZAK~ have been using subcaniers on FM for almost 40 years. The concept of subcarriers on EM stations was introduced in the 1930's by 'major" Almstrong4, He inventor of I;'M. \NCHRP`Phasc2.'p~\ NCHRP 3-51 · Phase 2 Anal Report A1-304

· Avoids R&D costs. Much of the hardware needed to implement a broadcast subcarner based system is already available off-the-shelf, thus avoiding the uncertainty, delay and cost of developing new technology. . No license is needed. Because subca~Tiers are considered a subsidiary service of an existing broadcast licensee, no further license is needed. The radio or TV station does not even have to notify the FCC Hat it is adding a subcarrier to its signal. · No regulations govern the use of broadcast subcarr~ers. So long as the subcamer is not used in support of an illegal activity, there are no regulations as to content or applications. ELI anal TV stations are existing, in-place facilities. Noting needs to be built in order to get subca~Tiers on the air. The equipment unique to subcarrier operation is compact, typically taking less than twelve inches of standard equipment rack space. Installation is simple, usually just a single cable from the subcarner generator to an existing connection on the broadcast transmitter. . Receivers can scan the band for a station carrying the subcarrier that Hey want to use. The number of radio and television stations broadcasting in any one area is limited (as compared with land mobile channels), making it practical to scan ad He stations in an area booing for one cat ng He subcamer of interest. Since aB modern EM and television tuners are synthesized, scanning is neither a technical nor a cost burden. Virtually all RDS receivers are equipped to scan in search of a specific RDS coded channel. ~ addidon, the frequency of many radios can be selects Ma commands from He RDS channel. · Broadcast stations blanket the country. The distribution of radio and TV stations follow the geographic population distribution accurately. Where Here are a lot of people, allele are a lot of broadcast stations. In addition, the land area of He U.S. with no FM or TV coverage is minute. . Broadcast signals are reliable. The economic incentive to keep a radio or TV station on He air is great. The revenue from advertising for an EM radio station can range from $50 to L;\NCHR~Ph~p'\ NCHRP3-51 · Phase2FmalReport A1-305

$500 per minute. For a television station, a one minute commercial can cost five to ten times more than for a radio commercial. · Subcarriers on FM and television stations have vast coverage areas. IBM and TV transmitters usually have Me most favorable locations in any region, often win tall towers built especially for Weir use. The effective radiated powers of art FM station can range up to one hunch kilowatts, TV station aural catners range from five to fifty kilowatts. · The incremental cost of adding a subearrier to a broadcast station is low, usuaUy between four and six thousand doBars. What is a Broadcast Subearrier? All broadcast stations, FM, AM and television, have the capacity to transmit subcamers. These subcarriers can convey audio or digital information. The best known class of subcarners are cattier on FM broadcast stations. Ong~naPy subcarners were used exclusively to transmit background music, but since the deregulation of FM subcamers by Me FCC in 1983, subca~Tiers on FM stations have found a wide range of applications. A convenient way to Mink of subcamers on FM or TV stations is as ultrasonic signals above the range of human heanng, like a dog whistle, carrying information along win Me FM programming. Listeners win conventional radios can not hear He signals; special receivers are required. The stereophonic program of an FM or TV station is transmitted in a similar manner. Subearriers on FM Stations Under die current FCC Rules, an F-M broadcaster has few restrictions on the programming or technical nature of the subcamers. By conventions, a "standard" background music style subcaliber on an FIRM radio station is a frequency modulated analog channel, has an audio frequency response of 50 Hz to 5 kHz and a signal-to-noise ratio of about 40 dB. This is about the same audio quality as an AM broadcast station. There is room for two of these channels on an I;M station operating in stereo, centered at 67 and 92 kHz. When used to transmit data, each L:~C~h~2.~6 N~3-S1 · P~2F~Re"n A1-306

of these channels can support up to 9600 bits/second digital ~roughput8. If the station operates in monaural, one or two additional subcarners may be accommodated. RDS Another type of broadcast subcamer in common use, especially in Europe, is caned RDS (Radio Data System). Originally RDS was designed to display Information on, and to exert control over, the automobile radio. The U.S. version, REDS (Radio Broadcast Data System), is nearly identical to European RDS9. In many ways it was an early ITS application, duplicating the functionality of Me German AR] traffic message alerting system. The basic implementation allows a radio to indicate whether or not the tuned station broadcasts traffic information as part of its programming, and whether the tuned station is currently broadcasting a traffic message. This information could be used to stop a cassette or CD and turn on the radio for the duration of We announcement. RDS radios typically allow the listener to use this information as a search criteria when scanning the band, stopping only on stations which broadcast traffic information. The original fonn of RDS was specifically tailored to European broadcasting and European driving needs. However, a U.S. standard, REDS, was completed in 1993. This document reflects the adaptation of RDS to Norm Amencan needs~°. "RDS" is used in this paper to refer to both Me European RDS and He U.S. REDS standards. RDS offers ITS applications the advantage of a proven system. It has been operational in Europe and parts of Asia for sever years. Many companies manufacture He needed transmission equipment and all the major automobile receiver manufacturers offer radios win RDS features. Because RDS is a mass market system, several semiconductor manufacturers offer inexpensive integrated circuits to implement RDS. RDS is a technically robust system. Its parameters were chosen for minimum impact on He main channel operation of He radio station and for a low bit error rate. The system has a record, verified by numerous operational tests 129~39~49~5 of having achieved these design gods. ;\NCHRP`Phase:.rp' ~NCHRP3-51 · Phase2F~nalReport A1-307

A significant drawback to RDS for ITS applications is its low data rate. The raw transmission rate is ~ 187.5 bits/second. If the channel is used in a manner consistent wad Be RDS standards, only a few tens of bits per second are available for discretionary use. However, many of the built-in functions of RDS are intended for ITS type activities and offer additional data capacity within Me RDS standard. TMC, or Traffic Message Channel, is a good example. It is an RDS code group (the basic units by which RDS functionality is allocated) designed for tankage independent traffic incident reporting. An important feature of TMC is its ability to make use of many RDS channels on venous radio stations, each of which may be specific to a geographic region. Such a multiplexing of the transmission capability by regions makes for much more efficient use of Me limited data capacity of Me Individual RDS channels. A major effort is ongoing by He ENTERPRISE consortium to broaden TMC into an International Traveler Formation Standard aUs). AS is an open, non-proprietary protocol that offers a largely medium independent and very compact code for exchanging traveler information. The widespread availability of low cost hardware and the robustness of the transmission technology make RDS work considering for any llS activity that could function with low, but reliable, data throughput. Traditional "SCA" FCC Rules place almost no restncdons on the technical nature of subcamers on FM radio stations. For this reason there are a number of subcarr~er systems either in limited use or proposed, Hat fall outside the standards of RDS or the de facto standards of background music type subcarners. The MrrRE Corporadon's STIC, NHK's DARC proposals and venous proposals for using single sideband suppressed carrier techniques for both analog and digital signals are examples of such systems. u`NCHRP\Phas~rp~\ NCHRP 3-51 · Phase 2 Fmal Report A1-308

Table A.~.7.3~1 Radio Data System (RDS) Groups and Functions . _ Group Function O Basic Tuning and Switching. Basic information about a broadcasters services, including alternate frequencies for this station, and whether or not this station ever broadcasts traffic announcements. 1 Program Item Number. The broadcaster may identify each program broadcast with a unique ID. _ 2 aadiotext. Text messages 32 or 64 characters long. 3 Location and Navigation. City, state, and grid coordinates of the transmitter, and Differential GPS data. _ . _ 4 Clock Time. Accurate time and date, broadcast once per minute. Automatically sets time display in receivers tuned to the station. _ _ 5 Transparent Data Channels. 32 Channels of unformatted data, 16 or 32 bits at a time. 6 In-house. Unformatted data transmission for private use by the broadcaster. 7 Radio Paging. Beep' digitals or alphanumeric paging 8 Tragic Message Channel. (under development) 9 Emergency Warning. Intended to augment' and eventually replace, the Emergency Broadcast System. 10 Program Type Name. Eight characters of text for broadcasters to identify their program category. 1 1-13 Reserved. . _ _ 14 Enhanced Other Networks. Used by European radio networks to inform radios and listeners about services offered by affiliated networks. 15 Fast Tuning and Switching. Brief information about a broadcast. The RDS system divides its functionality into the above 16 data groups, which may be used in any proportion and sequence that win meet a broadcaster's needs. Most of these groups win probably go unused in the U.S., as they were designed to support We needs of large European national radio networks. Over, more advanced features we probably remain unused because receivers equipped to take advantage of Hem are not yet available. Approximately ~ ~ of these groups are transmitted every second; anywhere between zero and seven of these may be left over after He broadcaster's needs are served. If an llS service were to lease 7 Transparent Data Channel groups L~`NCHR.~rp~\ NCHRP3-51 · Phase2FinalReport A1-309

(group 5) every second, Heir actual data throughput would be 224 bits per second. When considering any such novel subcarriers, it is vital that the broadcast system as a whole be considered. In order to be viable, a broadcast subchaser must operate without any interference to the reception of He regular broadcast of He host radio or television station. This is not a trivial requirement in light of He vast range of receivers in the hands of the general public. It is not enough for He subcalTier user to be able to say to the broadcaster Hat the subcamer transmission is "clean.~6" The assurance must be Hat in no class of receiver does the subca~ner generate any kind of spurious signal Hat would annoy He general public. In He case of background music type subcarners at 67 and 92 kHz on FM stations, the process of achieving compatibility with consumer receivers, especially stereophonic types, has been an iterative one. The 67 kHz subca'Tier has been in use for so long (almost 40 years), that most designers of receivers and receiver integrated circuits for the U.S. market take it into account. In turn, broadcasters have become much more careful about transmuting non-standard subcalibers. The 921dIz channel has come into usage much more recently, but that frequency was carefully chosen to take advantage of much of He protection designed for 67 kHz. These precautions have worked for most U.S. style radio stations using 67 and/or 92 Liz subcarriers. However, a few fine arts stations in the U.S. will not catty any subcarriers, claiming that their presence is audible to some listeners~7. It should be noted that in Europe, where traditionally FM broadcasting has an entirely different character than in the U.S. and consumer radios are designed with that difference in mind, attempts to use a 67 kilz subcamer have met with failurel9. When He Europeans designed RDS, non-interference with regular radio listening was a prime, possibly number one, design goal. The goal was met, although at He cost of reduced data transmission rate. For these reasons it is important Hat any proposed subcarrier that can not be shown to be technicalRy identical wad proven technology, must prove "audience compatibility" win a varieW of radio station programming formats. It would be easy for even a poorly designed subcarrier c;\NCHR~Phas~.rp~\ NCHRP 3-51 · Phase 2 final Report A1-310

system to not cause problems for the audience of a heavy metal rock station whose average modulation never falls below 70%. However, the same system might cause significant listener complaints if used on a classical music or jazz format fine arts radio station with an average modulation of less than 20%. The converse of these concerns is also an issue. The technical style of some radio stations can destroy the reliability of certain subcarr~er systems. For example, FM broadcasting in Japan is tightly regulated technically and not highly competitive, very much like traditional European broadcasting. It is suspected that several of Me subcamer systems Tom Japan, if tested on typical U.S. commercial FM radio stations, would not fare well. This strongly points up the need to test any new subcarner system across a range of U.S. radio stations types, including heavily modulated contemporary format stations. In Me past, Me results of several subcatner systems tests have been "loaded" to produce favorable results by Me skillful choice of test stations. The only way to avoid such skewing of test results is to try any proposed system on a variety of radio station types. TV Aura/ Based Subearriers Television stations also have the capacity to transmit subcaIriers on their aural carriers. A broadcast television signal consists of two completely independent signals (or "canters" as engineers prefer to call ~em): a visual and an aural. The visual earlier is an amplitude modulated wideband signal (about 6 MHz wide) cat ng the complex waveform of color video. The aural carder is frequency modulated by He sound portion of He program. In most ways, the aural cattier is identical to an FM broadcast signal. At many television stations the aural and visual signals are generated by physically separate transmitters. Subca~Tiers on a television station enjoy some significant technical advantages over subcarriers on an F-M station. TV stations generally have better technical facilities Han I;bI stations greater antenna heights, the best transmitter locations, and more radiated power. Because TV stations do not compete L:\NCHRP`Phase2.rp~` NIP 3-51 · Phase 2 Fmal Report A1-311

with each other to be louder2°, they use much less audio signal processing than most FM stations. Processing tends to interfere with subcamer operation. But most important is that Me sound channels of television stations are not 'packed in" to permit the most number of stations in Me same geographic areas. Thus, unlike EM, the coverage area of a TV sound channel is not limited by interference from other stations. An additional advantage Mat subcarriers on television stations have over those on FM stations is that in TV, no portion of Me main channel signal is taken away in order to "make room" for Me subca~Tier. In EM, the main channel must provide half of the additional modulation needed by Me subcarrier. This limits the amount of the signal Mat can be allotted to subcarrier operation. If the subcaliber on an F'M station requires ten percent main channel modulation (injecdon), Men Me main channel is decreased by five percent and the total modulation available is increased by five percent. This diminishes Me main channel's competitive loudness very slightly. In TV operation, all of the modulation needed for subcarners is obtained by increasing the total available modulation as needed. If the station is broadcasting stereophonic sound, Me available subcatriers are more or less defined by FCC Rules. If the station does not broadcast in stereo, its capacity to carry subcalibers is more than double that of a monaural FM station. SAP and PRO For TV stations operating in stereo, tile available subcamers are mostly defined by Me FCC22. The best known of these subcamers is Me SAP channel. SAP stands for "second audio program." It is a high quality audio channels, with characteristics approaching that of a monaural FM radio station. Most "high-end" television sets and VCRs Mat receive stereo sound also pick up SAP. Depending on the specific llS application, this accessibility by Me general public may either be a strength or a weakness. Although SAP was intended for carrying foreign language simultaneous translation of Me dialogue on the main channel, few stations use Weir SAP channel for this or any other purpose. Only noncommercial television broadcasters utilize Weir SAP consistently, mostly for descriptive narrations of Me visible action for Me blind. Few commercial stations use Weir SAP for any revenue producing activity. ;~NCHRE~.'pt\ NCHRP3-51 · Phase2F~nalReport A1-312

SAP is an excellent candidate for analog, sound ITS use. A commercial system is on the air in Los Angeles using Me SAP channel of a UHF television station to deliver fun time traffic reports. In addition to being available at home to anyone with a stereo equipped TV, the company sells a relatively inexpensive device that enables an auto radio to receive SAP in the car. While this adaptor fails to take fuB advantage of available technology to efficiently recover He SAP signal In a mobile environment, it works wed. The PRO, or professional channel, is Intended for use by He television station to provide internal one-way commuriicabons for venous news gathering and remote condor functions. Technically, it has about He same characteristics as a regular dial telephone circuit. Because it avoids He expensive use of cellular telephone to deliver special feeds of program to news reporters at remote sites, the PRO channel is often more valuable to He station Han He SAP channel. Because of its limited frequency response arid low injection level dunug stereo operation, PRO holds limited utility for ITS applications. The SAP and PRO channels are specifically authorized by the FCC for television stations broadcasting in stereo. It is likely Hat with a proper showing to He FCC, the subcarrier spectrum available above the stereo signal could be used in other ways more useful to ITS. For a television station not broadcasting in stereophonic mode, He FCC makes He entire subcarner spectrum available in He most versatile way24. While it is unreasonable to expect an FM station to forego operation in stereo, a reasonable economic incentive might convince a television station, especially a UHF one, to remain monaural. A monaural television aural cattier can accommodate a mix of several high speed data channels and audio channels as wed as conventional SAP and PRO. A variety of off-the-shelf equipment for transmitting and receiving SAP and PRO channels signals is available, but there are no starboard systems made for taking advantage of the expanded subcamer capability of a monaural television station. However, it is likely that some subcaliber systems intended for FM applications could be adapted for monad television. Figures A.~.7.3-1 and A.~.7.3-2 are He baseband spectra of typical FM and TV (aural) stations operating stereophonically. It is important to note Hat these are baseband spectrum plots, not L;\NC~Phase2rpr~ NCHRP 3-51 · Phase 2 Fmal Report A1-313

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plots of the radio frequency spectrum. This is not how these signals would appear if an RF spectrum analyzer were used to observe them. Rawer, it is how the detected wideband signals would appear displayed on a low frequency (20 Hz to 120 kHz) spectrum analyzer. The most notable difference between He EM and television baseband spectra is the stereo pilot frequency. FM stereo uses a 19 1~ pilot tone and an L`-R subcarrier at twice that frequency (38 kHz). the stereo pilot of a TV aural signal is at the video honzontal sync rate of 15.734 kHz. The L-R subcarrier is centered around twice that frequency (31.468 kHz). Another difference, not shown in the figures, is Hat He television L-R subcamer is companded for noise reduction purposes. Were the stations operating In mono, Hen He entire baseband region above He location of He stereo pilot tones (pilot tones are not used in mono operation) would become available for subcarner use. This is described in He table on page six. VBI 1 Another technology for transmitting data along win a television signal is vertical blanldng interval encoding, usually called "VBl." VB! does not employ subcalTiers on the sound cattier. Rather, it inserts data pulses (seen as bright dots on the screen) on the actual TV picture. The data is carried on scan lines of the television picture that are normally hidden by He mask of the picture tube. However, by using He vertical hold condom on a television set to "roll" the picture so that the black blanking bar (~e vertical blanking interval) at the top and bottom of He picture is visible, you can often see some VBI data. L;\NCHRP\Phase2.rp`` NCHRP 3-51 · Phase 2 FmaI Report A1-316

Services that employ VBI are variously caned: Teletext, Videotex, Viewdata, Ceefax, Oracle, and Closed Captioning. Depending on the exact technology used and the number of TV scan lines devoted to data, transmission rates of 1200 to 9600 bits/second or more, can be achieved wad VBI. VB1's greatest strength is that it can be distributed to a large number of stations easily. Once VB! data is added to the television picture wavefonn, it will go wherever Be picture is transmitted- up to a satellite, over a cable TV system, etc. It takes a special and somewhat expensive piece of equipment to remove a VB] signal from He picture. This is not Be case with subcaITiers, where a separate transmission channel is needed to catty Be information, and insertion equipment is needed at each transmission point. ABE has some serious drawbacks, especially for mobile use. The data bits are pulses (bright dots) less Pan 200 nanoseconds long. Therefore it takes very little multipath to destroy the VB! data much less than to damage data on a subcarner. Informal tests show VBI not to be viable in a mobile environment. The complexity of receiving equipment needed to recover VB] data is much greater, and therefore more expensive, Ran Nat needed for subcalibers. In spite of these drawbacks, VB! bears watching because of its ease of wide area distnbution. It is possible that a technical breakthrough will make VB] practical for mobile applications. Often the cost of complex technology drops significantly with large volume demand. VB! should also be considered for any ITS application that needs transmission of data to a fixed location such as rem time maps showing weaker and road conditions to rest stops along major highways, or mass Posit arrival information to pickup points. Suboarriers on AM Radio The least known and least developed subca~rier technology is on AM radio. The occupied bandwidth of an AM broadcast station is much less Han an FM or TV station 15 kHz as opposed to 240 kHz. There is no spectral room for a high speed '`ultrasonic" data chaIme] on an AM canter. Subcatiiers for AM radio stations are subsonic- below He 20 to 30 Hz cutoff for human perception of low frequencies. c:\NCHRP`Phasc2.rp`\ NCHRP 3-51 · Phase 2 Fmal Report A1-317

Such low frequency operation limits He data rates possible with AM subcarIiers to typically less Man 100 bits per second. AM subcarriers have never been widely used, as their low data rate has limited Weir applications. In addition, questions about compatibility between subcamers and AM stereo became an obstacle to Heir widespread use. Today, subcamers on AM stations bear careful consideration. Although Heir data rate is low, it is comparable USA He number of bits per second available in an RDS transmission after He broadcaster-specific parts are accounted for. AM radio signals are much more robust Han Heir FM counterparts. Medium wave AM signals penetrate buildings much better Han very high frequency FM, and multiparty is a virtually unknown problem for AM. For reliable automobile reception beyond He radio horizon and in mountainous ten ain, AM broadcasting is an ideal choice. An additional consideration is He low cost of AM receivers. Integrated circuit AM receiver chips are mature and very inexpensive. A subsonic data decoder could probably be -added to such a chip for lithe or no cost if a sufficiently large quantity could be ordered. While compatibility problems between subcamers on AM stations and stereo operation still exist, time has significantly altered He importance of this issue. Stereophonic operation has failed to achieve He dominance for AM stations Hat it has for I;M, possibly because much less music is being broadcast on AM In He United States. AM today has become mainly a medium for delivering information such as news and talk. AM broadcasting is in a state of economic decline as compared wig FM. Therefore, the potential revenue from subcalTier operation may be more attractive to an AM station owner today Man it was ten years ago. Subcarr~ers on AM broadcast stations, in spite of Heir low data rate, offer ITS an inexpensive way to deliver digital infollllation to automobiles. This may be useful in low population density areas where there is not a large quantity of data to be transmitted. Subcarriers on AM offer potential as a "dispatch" channel even in densely populated cities. ~:\NCHRP\Phasc:.rp~` NCHRP3-51 · Phase2F'nalReport A1-318

Data Hates The concept of data transmission speed ranks with "miles per gaBon" as an abused and misused term. Too often it is He subject of "specsmanship." It is important to differentiate between the information rate of a transmission channel and its signaling speed. Signaling speed is the "raw" data rate of the channel in bits per second. It is the most frequently quoted parameter of a data transmission system because it is the largest number that can be legitimately provided, and therefore the most impressive. However, it can be misleading. It is also necessary to know the bit error rate, or BER. Often a data transmission specification Will list a high data transmission rate and a favorably low BER, however, a footnote will say that He BER is achieved with "error correction." That means Hat some portion of the data capacity of the channel was traded off to encode He data in order to lower He effective error rate. Between 50 and 90 percent, or more, of total channel capacity may be given up in this manner. If one-half the capacitor of a 9600 bitJsecond data channel is traded for error correction, then the information rate is really 4800 bitsJsec. If a 9600 bit/see channel is data corrected to carry 4800 bits/second urge an error only once every 100,000 characters and a "raw" 4800 bit/see channel web no error correction produces He same one error ever, 100,000 characters, Hen there is no advantage to the 9600 bit/see channel. Coverage of Broadcast Suboarriers For most wireless systems Here is no tougher question than, "what distance coverage can expect?" Measure an Existing Signal A broadcast subcamer based system offers the most accurate answer possible because almost always He proposed subcanier will be added to an existing broadcast station. If exact coverage data is needed, then it is only necessary to make coverage measurements on the proposed station. By observing an excising subcamer (such as He stereophonic difference channel for FM or TV) L.:\NCHRP`Ph~p`` NCHRP3-51 · Phase2FmalReport A1-319

on the station under Be same receiving conditions as Be proposed system, a very accurate coverage map can be denved. Calculate Coverage If mode} based coverage is sufficiently accurate, Men several organizations can plot detailed coverage maps25. Note Hat for any modeling service to be of value, Be receiving conditions must be specified. Broadly, reception may be: 1] At a fixed location with a random antenna. This would be typical of someone at home with a table model radio. 2] A fixed location win an outdoor antenna. A commercial installation such as a ton plaza building or a atop a pennanent variable message sign might fall into this category. 3] An automobile installation with a whip antenna somewhere on Be body of Be car. 4] A personally canted receiver such as a pager or a walkperson type radio. Rules of Thumb There are some very rough approximations Hat can be useful for making educated guess about the subcaliber coverage of a FM radio station. To make these guess you need sever pieces of information: The class of FM station - for commercial stations Hey may be class A, B or C. Class A stations are local service stations u id coverage of ~ to 12 miles. If the antenna is around 300 feet HAAT, then the coverage will be toward He ~ mile range; if the HAAT is around 500 feet or more, then it win cover around 12 mites. The height of the antenna above average terrain. This is usually referred to as HAAT (height above average terrains. Lastly, what He receive situation is, as described in types ~ through 4 above. These guess are for a radio at home with a random antenna - situation 1. For a car radio web an whip antenna, expect a few more miles. Win a personal radio, expect significantly less coverage - maybe 50% less. Coverage with an outdoor beam (yagi) type antenna is a special case. Distance is mostly a function of He heights of the transmit and receive antennas and almost independent of He effective radiated power. L:\N~Phasc2.rp'` NCHRP 3-51 · Phase 2 Fmal Report A1-320

Obtaining Broadcast Subearriers Leasing a subcarner from a broadcast station is usually a straightforward business transaction. However, some insight into the broadcaster's Linking might help in securing a subcaliber. The best analogy for understanding a broadcaster's attitude toward his or her subcarner is to think of it as real estate. The subcarner is a small piece of property belonging to the station that you wish to lease. It is a section of a much more valuable plot of land, the main channel as received by the general public. The broadcaster is depicted to receive revenue for this mostly unused land, but must be assured Cat noting you do will have any negative impact on the much more Important things that are done on the main plot. If the broadcaster can easily understand what it is you want to do with the subcamer, because it is Be same thing that he sees his neighbors doing or because it has been on that station before, then the contract won't go on for pages with technical details. On the other hand, if you want to do something novel, expect Mat a smart broadcaster is going to ask a lot of tout questions and want a great deal of contractual reassurance. Just as in real estate, trying to place value on a lease can be difficult. Valuing a subcaITier lease is even harder because Were is no requirement Rat over broadcasters make public how much they are leasing their subcarners for. In some cities the monthly rental for a similar subca~rier on similar radio stations can range over a five-to-one ratio! If you need to lease a broadcast subcarrier and have no insight into the value of subcatTiers in your cider, it is suggested Hat you obtain outside help. Outside help may be as close as a retired broadcast executive. However, the most common source of assistance is to retain an attorney experienced In working with radio stations. These are communications lawyers and are usually based in Washington, DC, because that is where He FCC is. The Federal Communications Bar Association publishes a directory of its memberships. In addition to providing assistance in obtaining a subca~Tier, a communications lawyer can be of great help in negotiating He details of He contract. Often communications lawyers are comfortable win He technical aspects of subcamer leasing and can help win Cat portion of the lease as well. u\NCHRmPh~2~p'` NCHRP 3-51 · Phase 2 F~1 Report A1-321

Much of the information above may seem specific to commercial broadcast stations it is not. Often non-commercial stations can be more complex to deal with than commercial stations, even if when it is another government agency wishing to lease the subcamer. For example, non- commercial broadcast stations are permitted to lease their subcarners, on the open market, for profit. This makes subcarners about the only commodity that a non-commercial station has to seU. So don't expect a station to give up its subcaliber for ITS, however noble the project, for less than market price. For non-commercial FM radio stations, Me visually handicapped have a legal right to preempt one subcarner for a reading seance if any are being used for commercial purposes. Public TV is about Me only group of television stations making practical use of Weir SAP subcarner by providing narrations of Me visual action for the blind. ~ many cases this work is underwritten by various philanthropic and service organizations in the commu~iit,,r. The Future The initial appeal of broadcast subcarriers for ITS is as a "quick fix;" a way to jump start ITS without waiting for the cumbersome allocation process to catch up to ITS's need for radio spectrum. However, subcamers could also fill a long term need for ITS. SubcalTiers may not have the data bandwidth that the more sophisticated ITS applications need, but they will always be there as channels to provide basic functions as well as act as a common dispatch channel. Multiplexing ITS information over a number of broadcast subcamers would allow He system to grow flexibly, adding stations as additional bandwidth becomes necessary. Rural applications might be served well into the future by a single IBM subcarner, while urban regions could make use of the larger number of stations found there. This multiplexing could easily split up a w~deband data stream by region or application, and let the receivers scan the band for the ~nformadon of interest. Broadcasting is not a stagnant technology. Bow radio and television are on the brink of major technological change. IV is preparing for the high definition (HDTV) revolution. Radio expects approval on some form of digital audio broadcasting (DAB) soon. Bow of these will be digital technologies, and each will include auxiliary, non-program related data channels. L::~.NCHRP\Phase2.rp~\ NCHRP 3-51 · Phase 2 Fmal Report A1-322

DAB and HDTV will provide the broadcast subcamers of tomorrow. It is reasonable to expect Hat their data channels will be faster and more multiparty resistant than today's mostly analog subcamer channels. Because DAB and HDTV are in the earliest stages of definition and no standards have yet been set, the unique opportunity exists to influence these new systems to include features specific to ITS needs. The rRs community should make its needs Worm to broadcasters and He FCC. The most visible way to influence these new media to serve He needs of ITS is by filing formal comments wig the FCC on DAB and HDTV proceedings as Hey are opened for public comment. Much of the proceedings and aB notices of comment penods are announced in He Federal Register. A.~.7.4 Commercial Wireless Services Cellular is a commercial wireless telephone service that ong~nated in 1983 and has sustained a rapid growth rate to approximately 30 million subscribers in 1995. Personal Communication Services (PCS) are experiencing rapid development due to spectrum aBocations by auction in 1994/1995. Cellular has been predominancy an analog service with digital services emerging only recently, while PCS has been conceived as a digital service. In addition to providing potential commercial wireless services, cellular and PCS offer technologies and design methodologies that can be applied to provide important private communication capabilities for rrS-related applications. As an example, many products developed for 902-928 MHz ISM use components developed for 8007900 MHz cellular products. Perhaps the biggest technological advance in cellular has been in the understanding of propagation and how to increase system capacity Trough frequency reuse in cells. This cellular concept is illustrated in Figure A.1.7.41. Each cell is assigned a group of unique baselmobile transmit frequencies that are not reassigned (i.e., reuse) in adjacent geographical cells except at sufficient distance so that propagation loss is sufficient because the remote signal power is sufficiency attenuated so as to not adversely interfere. The remote signal in He local cell is referred to as "cochanne} interference" (i.e., same frequency interference). L;`NCHRE`Phase2~pr\ NCHRP3-51 · Phase2FmalRepo}t A1-323

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Within a cell, a mobile subscriber is assigned a frequency pair (i.e., transmitJreceive) by Me base station. If Me subscriber travels to an adjacent cell, a "hand-off'' is accomplished from Me base station in He departing cell to the base station in He receiving cell. Call setup and control are handled by a control infrastructure. A key element is control of transmit power so interference can be minimized. A key parameter in cellular system design is camer-to-interference (C/! relationship). For the U.S. standard 30 kHz channel spacing, C/T is 18 dB. Basic parameters for U.S. AMPS cellular systems are presented in Table A.~.7.4-~. Table A.~.7.4~1 U.S. AMPS Cellular System Parameters Parameter | Value Power Base 300 watts 7 watts ~ _ _ ~30 kHz Channels Total 7 cell reuse be_ Type 5~m Analog _ _ ~18 dB Cochannel (same frequency) ~Frequency (2 carriers) Multiply User Access Frequency The U.S. Advanced Mobile Phone System (AMI'S) was placed In service in 1983, after several years of development. In its early days, AMPS was primarily for automobile installation, but rapidly transidoned to hand-held portables with lower power, to conserve battery life. Subscriber growth has been exponential so Hat capacity is not keeping pace with demand, especially in large metropolitan areas. Cellular capacity can be increased In several ways: Employing smaller cells by cell splitting and using lower power. Cell sector~zation web directional antennae. L.`NCHRP`Phase2.rp~\ NCHRP3-51 · Phase2FmalReport A1-325

Use of Time Division Multiple Access (TDMA) digital modulation which permits multiple ~ . users on one frequency pair. · Use of Code Division Multiple Access (CDMA) which permits multiple users on one frequency pair. CDMA is a form of spread spectrum digital modulation (see Section A.1.3.4). Competing standards have emerged in bow the cellular and PCS services. Both TDMA and CDMA are digital modulation techniques and requure speech codecs that digitize and compress the analog speech signal. The quality of the speech codec Algonquins is a significant determinant of die user's perceived quality of service. These digital modulation techniques, when widely deployed, can efficiency support data without a modem. None of these competing digital standards have substantial current U.S. deployment in either cellular or PCS. AMPS is still dominant; however, PCS win be deployed more as competitive pressures win undoubtedly force an eventual transition to digital cellular for added capacity and additional features. Table A.~.7.4-2 presents He primary cellular/PCS systems in Be U.S. and key operational parameters. It should be noted that Global Systems for Mobile (GSM) is an adaption of Be European system for emerging PCS services and has been selected by several PCS service providers because equipment is available for rapid deployments. CDMA has been selected by several of Be service providers because it debatably offers increased capacity. Unlike analog cellular, digital cellular and PCS have multiple deployed standards. Time and the marketplace will determine user acceptance. Cellular Digital Packet Data (CDPD) is a service available from analog cellular providers, which offers packet data capability in the cellular bands. CDPD Besets bursty packet data on idle cellular analog channels. Because it fits data between voice conversations, CDPD has not yet (early '96) verified that it will operate satisfactorily in overloaded metropolitan areas. S~m~lar CDPD services will be offered via digital cellular/PCS bands and the already digital modulation may provide more cost effective services and equipment. The PCS bands are being auctioned and few are operational in '95/'96. The allocated frequency bands are presented in Figure A.~.7.4-2. It should be noted Mat Be FCC has allocated bow t.:`NC~Phasc:.rpr\ NCHRP3-51 · Phase2FinalReport A1-326

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licensed and unlicensed bands. As previously noted, PCS will be digital on initial deployments. It should also be noted that the FCC PCS frequency avocations constrain two unlicensed bands. One is asychronous for packet data applications and one is isochronous (equal delay) for potential voice/video applications; such as wireless PBXs. Two wireless packet data services offer commercial capabilities using He Specialized Mobile Radio (SMR) frequencies near 800/900 MHz, offering coverage to about 90% of urban business areas. Advanced Radio Data Infotmabon Service (ARDIS) is available in more than 200 metropolitan areas. RAM Mobile Data (RAM or RMD) service is available In 216 metropolitan areas. ARDIS and RAM have more Han 52,000 subscribers nationwide. Table A.~.7.4-3 provides an overnew of these services and, for comparison, equivalent information on CDPD. Table A.~.7.4~3 Commercial Wireless Data Services ARDIS ~ RAM ~ CDPD Mobitex Architecture) Data Rate | 4.8 kbps | kbps | 19.2 kbps 19.2 kbps Frequency Band | SMR | MR | Cellular l 800/900 MHz 800/900 MHz 824 - 894 Mbps Number of Channels 10 - 30 Cellular frequencies each Metropolitan area Coverage ~410 MSA 210 MSA 50 MSA (MSA- Metropolitan Service Area) Comment ~ Proprietary protocol ~ Proprietary protocol ~ Public protocol Analog modems over c~rcuit-sw~tched celdular phones are frequently used for wireless data transmissions. These are typically the V.32/V.34 wireline modems; however, He cellular telephone network has different characteristics from He standard wired network and special protocols are required for reliable commun~cabon. Two ceDular-specific error correction protocol standards are employed: 1) Enhanced Throughput Cellular (ETC), developed by AT&T (now Lucent Technologies); and L;`NCH~Phase2.~p~\ NCHRP3-51 · Phase2FinalReport A1-330

2) Microcom Network Protocol lO Enhanced Cellular (MNPlOEC), developed by Rockwell International. Both of these protocols are extensions of the ITU V.42 error control and correction protocol. It should be noted that, even with special cellular protocols, He throughput (byte per second) can be substantially less Can rated land line circuit performance. In addidon to the proliferation of wireless communications services, the wireless explosion is providing many standard "air interfaces" Mat could prove useful and adaptable to ITS applications. A.1.7.5 ISDN Integrated Services Digital Network (ISDN) is a digital dialup telephone service that was conceived to provide end-to-end digital telephone service. After years of hype and unrealized potential, ISDN appears to have achieved some recent successes largely as a result of demand for higher speed (compared to dialup modem) access to Internet services. It is also widely used by the radio broadcast industry for higher quality voice transmission from remote sites (e.g., sports arena, etc.) and win offer similar benefits to rRs. For years, He commercial telephone network has employed digital switching, multiplexing (i.e., T! digital hierarchy), and transmission. However, the TWP connecting He Central Office (CO) switch to subscriber telephones has been analog as depicted in the lower part of Figure A.~.7.5-! ISDN essentially extends the digital DS-O (or B channel In ISDN terminology) to He subscriber premise as depicted In He upper part of Figure A.~.7.5-~. A D (or data) channel is also provided to serve the equivalent telephone signallcontro] fimctions such as on/off hook, DTMF dial tones, busy signal, etc., tones Hat are provided "in-band" on He standard analog telephone circuits. Additionally, this D channel may also serve as a packet data channel for packet services, although most current services appear to use B channels. L;mC~Phasc2~p~\ NCHRP3-51 · Phase2FmalReport A1-331

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ISDN is basically a WAN service that is available In two forms: Basic Rate Interface (BRI). Primary Rate Interface (PRO. BR] provides the following: · 2 B Channels (DS-O, 64 kbps) for a total of 128 kbps. · ~ D Channel at 16 kbps. Deployment over existing telephone company TWP loop plant by providing ISDN terminals at bow the customer premises and Be service CO (also in Figure A.~.7.5-~. PRI provides: Essentially DS-] service at 1.544 Mbps Up to 23 DS-O channels available within the DS-l frame, (although over rates can be supported). ~ D channel at Be DS-O rate of 64 kbps. · This requires special 4-wire TWP circuits and repeaters for longer distances (the equivalent of T1 DS-1 circuit requirements). N  L:\NCHRP\Phase2.rptN NC~3-51 ~ P~2F~Re ~A1-333

Endnotes: 1. The infrastructure can be a regional traffic center, an incident center, a real-time map update facility, etc. 2. The Communications Act of 1934 (as amended) requires He FCC to judge all requests for radio spectrum by determining if the need is "in the public interest, convenience or necessity." 3. SCA, or Subsidialy Communications Authorization was a FCC description that was deleted from the FCC Rules (47 CI;R 73) in a rule making proceeding in 1983. It was replaced by the description Subsidiary Communications Service, but the initials SCS never caught on. In any case, these terms are very narrow and exclude F'M RDS and various TV aural subchannels. In addition, neither SCA nor SCS are descriptive of the channels. Calling these channels "broadcast subcamers" is both inclusive and technically descriptive. 4. Edwin H. Armstrong, "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation," Proc. of the I.R.E., Vol 24, No. 5, May 1936. Repunted; Jacob Klapper ed, Selected Papers on Frequency Modulation, Dover, New York, 1970. 5. A minor exception to this is in the case of non-commercial FM stations that must, if they use any subcarriers for profit making activities, make an additional one available for use by radio reading services for the blind. 6. Effective radiated power is the transmitter power output available at the antenna multiplied by the gain of the antenna 7. This is a holdover from ten years ago when there were FCC Rules governing subcarrier technical operations. Today there are no such rules, but the practices continue from 'Force of habit." 8. There is a large distinction between "throughput" or the information rate and the signaling speed. Depending on Me level of error correction, the signaling speed may be several times faster Wan the data throughput. The later section "Data Rates" discusses this issue in more detail. 9. T. Beale and D. Kopitz, " RDS in Europe, REDS in Me USA ~ What are Me differences and how can receivers cope win bow systems?," European Broadcasting Union (EBU) Renew - Technical, Spring 1993, pages ~8. 10. "United States REDS Standard, Draft No. 2.0, NRSC Document, August 1, 1992" National Association of Broadcasters and The Electronic Industry Association. 11. A. G. Lyner, '~xpenmental Radio Data System (RDS): A Survey of Reception Reliability in the UK," Report BBC RD 1987/17, British Broadcasting Corporation Research Department, Engineering Division, Nov 1987. 12. Ibid. 13. "IKE Colloquium on 'The RDS System - Its Implementation and Use' (Digest 128)"; IKE, London, UK; Dec 1988. 14. K. H. Schwaiger and J. Mielke, 'prowess With He RDS System and Experimental Results," European Broadcasting Union (EBU) Review - Technical, No. 217, June 1986, pages 150~158. 15. F. Stollenwerk and N. Pfeiffer, 'first Operational Results of the Radio Data System (RDS)," lIG-Fachberichte, Vol 106, Pages 123-128, 1988 (In German). L.\NCHRP\Phasc2.'ptY CHAP 3-51 · Phase 2 Fmal Report A1-334

16. J. H. Paffenbarger, "Optimized Implementation of SCA Subcarriers for Minimum Degradation of FM Stereo Reception," Proceedings: 41st Annual Broadcast Engineenng Conference; 1987, National Association of Broadcasters, Washington, DC. A contrary position is taken by Paffenbarger. However, the FM station discussed is a fine arts type of station much closer to the traditional European norm than the U.S. 17. This may be a self seeing position for some non-commercial fine arts stations. Non-commercial FM stations are obligated by the FCC to provide subcanier service to reading services for the blind if they make commercial use of any of their subca~riers. Objecting to subca~Tiers on technical grounds offers an credible way to refuse being forced to "give away" one of their subcarriers. 18. Ibe character of broadcasting, especially FM, is changing in Europe win He Mowing movement toward private ownership of radio and television stations. These new stations are evolving very much in He style of U S. commercial broadcasting. 19. D. J. Thyme, 'the transmission of Two Program~s From Band ITEM Transmitters: an assessment of 'Storecasdng'," Report BBC RD 1976ll4, British Broadcasting Corporation Research Department, Engineenng Division, June 1976. Reprinted in the European Broadcasting Union (EBU) Review - Technical, No 161, February 1977, pages 20-30. 20. In the presence of competing signals, as is the case in the FM band, the greater the average deviation (loudness), the greater and more reliable will be the coverage of the radio station. 21. The visual portion of He TV signal is much more susceptible to interference from other visual signals, so it sets the spacing requirements between stations. The aural carrier is significantly more resistant to interference than the visual, so it gets a "Bee rice" in terms of interference Tom other aural signals on the same channel. In addition, because the TV sound channel is adjacent in frequency to Be much wider band visual signal, interference from stations on adjacent channels is not an issue. This contrasts wig FM stations, for which adjacent and co-channel interference is the major factor in limiting coverage. 22. "OET Bulletin No. 60, Revision A"; Office of Engineering and Technology, Authorization and Evaluation Division; February 1986; Federal Communications Commission. 23. The frequency response is 50 Hz to 101tHz, with a signal-to-noise ratio better Han 60 dB. 24. The FCC Rules - 47 CORK 73.682(c)~1-9) provide Hat a television station may use non program related subca~riers from 16 kHz to 120 1~z at a total deviation not to exceed 50 kHi. 25. Data WorId or ITS Boulder, div of NIST. 26. The Federal Communications Bar Association, 1150 Connecticut Avenue N.W., Swte 1050, Washington, DC 20036. Telephone (202) 833-2684, fax (202) 833-1308. L;\NC~.rPtN NCHRP3-51 · Ph~2F~RePOrE A1-335